Fic: Cross Product, Part 2
Fandom: Stargate (Atlantis/SG-1 cross)
Title: Cross Product, Part 2
Author: Quasar
Rating: PG-13 for this part, NC-17 eventually
Pairing: McKay/Sheppard
Spoilers: specific references up to Duet, vague ones up to Allies
Date written: July 2006
Length: ~5,000 words for this part
Summary: McKay interrupts Carter and brain-melds with Zelenka.
Link to Part One
A day and a half later, John was in Colorado Springs, feeling punchy from too much caffeine and not enough sleep. The little Mustang, despite its battered appearance, had performed like a dream, and he had lost some of his tension as the miles slipped by. Now he was remembering everything he had to worry about. Was he about to face down a real -- and really angry -- general, or was he about to blow this fake world out of the water?
He'd stopped at a little coffeehouse just at the edge of town on the road to the Cheyenne Mountain complex. He was contemplating his strategy over capuccino and a slice of spinach-artichoke quiche when Dr. Daniel Jackson walked in. John hadn't gotten to know the man well in Antarctica, but he had lumped him in the same class as McKay: brilliant, excitable, and near-impossible to draw away from his work. John was definitely wishing he had Rodney here to untangle this bizarre situation. But given their similarities in disposition, maybe Jackson was someone who would listen with an open mind.
He watched as the archaeologist ordered a large double espresso and sat down with a huge leather-bound tome balanced on his knees. Standing and unconsciously tugging at his rumpled shirt, John considered the best way to approach the man. He was just crossing past the doorway when someone entering bumped into him.
It was McKay.
John's jaw dropped. "Rodney! You're here too? Thank God, I could use the help." He started to clasp McKay's upper arms, but the scientist was pulling back and lifting his elbows, and somehow John ended up grabbing him by the ribs instead. It seemed only natural to slide forward and give him a hug.
Natural to John, but apparently not to Rodney, who stiffened and pushed him away with an appalled look.
"How did you get here?" John asked. "Do you know how to get back?"
"Back?" said McKay weakly, his eyes flashing over Sheppard's shoulder.
"I take it this place isn't real, then?" John blew out a breath in relief. "That's what I figured, but I wasn't sure. I'm glad to see you -- I thought I was all alone here."
"Um . . ."
Hollow-headed with exhaustion, John didn't notice that he was doing a lot more than his usual share of the talking. "What did you do, stick your head in that device to come after me, after all the warning me about how dangerous it was? I just hope you've got some kind of back door ready to let us out of here, because I haven't had any luck thinking myself out so far."
"Hi, Rodney, is this a friend of yours?"
John turned to find Jackson at his elbow. The man seemed very mild-mannered, blinking at the two of them pleasantly, but something about his stance raised John's hackles. He automatically started to place himself between McKay and the threat. "I work with Rodney," he answered, and held out a hand. "John Sheppard."
Jackson smiled but didn't shake. "Daniel Jackson."
"Yes, I know --"
"Daniel, I've never seen this man before in my life!" McKay said, in tones of near-panic.
John's head whipped around. "Wait, what? I thought you entered the simulation to help me out!"
"Simulation?" Jackson asked quickly.
John stepped back to get both of them in view, but Jackson shifted to flank him without seeming to do it deliberately. John realized the faint threat he sensed was directed at him, and he suddenly recalled that the quiet archaeologist effectively had more combat experience than many veteran Marines.
Except that this was just a virtual representation of Daniel Jackson -- wasn't it?
"What are you talking about? What simulation?" McKay demanded.
"Well, this, uh, all of this." John waved vaguely at the cafe. "This isn't real, is it? It can't be real." After all, Rodney had appeared right after he wished for him.
"Did you forget your little pills this morning? Of course it's real!"
Jackson squinted and rubbed his nose. "I've always found it simplest to assume things are real until I see evidence to the contrary."
John shook his head in confusion. "But it doesn't make any sense. If this is really Earth, why is everything different? And how did I get here from Pegasus?"
"If this is Earth?" Jackson repeated, at the same moment that McKay said, "Pegasus?"
"Yeah, you know, a galaxy far, far away? Home of Atlantis?"
There was a moment of stunned silence, and John wondered if he shouldn't have mentioned the Ancient city. But if the aliens creating the virtual reality wanted to know about Atlantis, that could be the key to cracking their illusion.
Assuming it was an illusion. He still wasn't sure about that.
McKay looked around the mostly-empty cafe before hissing, "How do you know about --"
"Atlantis is, is a myth," Jackson interrupted.
"Yes, right, of course, a myth," McKay said quickly. "Whereas this, here, Earth, is real. Are the hair gel fumes making you confuse fantasy with reality?"
"No. No, this doesn't make sense." John stumbled back until he hit a chair and sat down. "If this is real . . . if this is real . . . but it's all wrong. Damn, why is it wrong? My head hurts." He rubbed at his temples.
"What precisely do you think is wrong with this, um, this world?" Jackson asked quietly.
"History is wrong. I'm wrong -- I'm not supposed to be on this planet at all. And you don't recognize me, and McKay acts like I'm an axe murderer or something -- it's all just wrong!"
Jackson squinted at McKay. "You know, this seems sort of familiar."
McKay nodded. "It almost sounds like he's describing --"
"-- an alternate reality," they finished in unison.
"A what?" John asked, but at that moment the cafe door opened.
A couple of uniformed men walked in, nodded to Jackson and took up positions looming over John with their hands poised over their sidearms. "I'll have to ask you to come with us, sir," the older one said.
John felt strangely as if he'd just screwed up a first contact mission.
-----
"So, let me get this straight." Seated at the conference room table, Sheppard looked between Rodney and Elizabeth. "These . . . Ancient aliens you're talking about invented some gates for traveling between planets."
"Stargates, yes," said Elizabeth.
"And they left one on Earth."
"Two, actually," Rodney said, garnering annoyed looks from the others. "But we don't need to go into the details just now."
"And the Air Force discovered this gate thing and started sending expeditions to other planets."
"Not just the Air Force . . . well, yes, basically." Rodney subsided under combined glares.
"And we're on another planet right now."
"That's right." Elizabeth smiled at him.
"You might notice the gravity is just a little lower than Earth's, by about three percent."
"He doesn't need to know every detail at once, Rodney," Carson protested.
"Come on, he's a pilot! He notices things like this. It's the simplest way to prove that what we said is true." Rodney turned back to Sheppard. "The other planet, with all the sand, that one had a gravity almost fifteen percent higher than Earth's."
Sheppard blinked. "I just thought my vest was loaded down."
"If you had dropped something, or tripped, you would have noticed that the acceleration --"
"Enough, Rodney," said Elizabeth. "I think he believes we're not on Earth."
"We're on -- in -- Atlantis," said Sheppard, returning to his recap.
"Yes."
"A floating city built by those same aliens."
"Actually, they were physically indistinguishable from humans, with differences primarily noticeable at the genetic level," Carson began, then noticed that Rodney and Elizabeth were glaring at him now. "But, yes, not originally from Earth."
Sheppard was distracted. "Wait, why would they look like humans? Is there some reason for that?"
"Well, technically we're descended from them," Carson said. "So are the races of the Pegasus Galaxy, like Teyla and Ronon here."
Sheppard turned to look at the other two members of the team. "You guys are aliens?"
"We are not from your Earth," said Teyla gravely.
"Whoa," said Sheppard. Then he looked back at Rodney. "But none of this explains why I'm here."
"Well, you -- or rather, our Colonel Sheppard -- is part of the Atlantis expedition. He has a gene which lets him interface more efficiently with some of the Ancient technology. We found a device on that desert planet, and Sheppard activated it by accident, and . . . it switched you into his place. I'm still working out the details of how that happened, and we need to understand before we can try to do anything about it." Rodney frowned and stood up. "In fact, I should be getting back to my lab. Zelenka must have finished going over those scans by now."
"I'll want an update before dinner," Elizabeth called after him as he headed for the door, and he waved a hand in acknowledgment. Behind him, she said. "Teyla, Ronon -- could you show Mr. Sheppard around, please? Make sure he doesn't get lost?"
-----
John was locked in a mostly bare room under Cheyenne Mountain. All his personal effects had been removed and he was wearing fatigues with no insignia, but on request he'd been given a pad of paper and a soft-tipped pen. Now he was sitting on the end of the bunk with the notepad on his lap. On the top page he had drawn two columns: REAL and NOT REAL.
In the NOT REAL column he had written "wrong history," "wrong body," "wrong planet," "instantaneous intergalactic transport?" "thought about surfing -- ended up surfing," and "wished for RM -- RM appeared." In the REAL column he had written "feels real," and "can't control it." He put a question mark after the latter, with arrows to the surfing and RM items in the opposite column. Frowning, he added "RM says it's real." Then he crossed that out and wrote "all Cretans are liars" underneath.
With a muttered curse he ripped off the top page and headed the next CRAZY and NOT CRAZY. He stared at the paper for several minutes before scribbling "see page 1" and dropping the notepad to his side. He flopped back on the bed and lay with one arm across his eyes.
He heard his door guard greet someone and sat up just as the door opened. General Jack O'Neill came in and eyed John curiously. He stood quickly and saluted.
O'Neill waved a hand vaguely. "Colonel Sheppard, I presume?"
John blinked. "That's right."
"And from that phone call I guess you know who I am?"
"Yes, sir."
"McKay here thinks you're from some kind of parallel universe." O'Neill glanced at the door where McKay was hovering uncertainly. "Oh, come in and shut the door!" he snapped.
McKay came in, but kept the bunk positioned between himself and John.
"Well?" said O'Neill.
"Uh . . . Rodney is usually right, sir. But there's a lot that doesn't make sense."
"You think? So what else is new?"
McKay retrieved the discarded page of paper from the floor. "Wrong body?" he read. "Instantaneous intergalactic transport?"
"Yeah," said John. "Those are the parts that don't seem to fit with other reports I've seen about alternate realities."
"And based just on that, you decided this was some kind of virtual environment?" McKay's tone implied that would be a monumental feat of stupidity.
John shrugged, relaxing under the familiar weight of McKay's sarcasm. "Well, at least I've encountered those before. And there were some coincidences that made me wonder. You know, like the black cat in the Matrix."
"Oh, please! That movie had to be the most appalling exercise in illogic I've ever seen."
"It wasn't that bad," John protested.
"Human beings -- drugged humans with atrophied muscles -- as energy sources? Their nutrition and maintenance would require far more energy than the minimal heat return. It's a basic principle of thermodynamics!"
"Okay, so the premise had some flaws, but the movie was internally consistent. Mostly."
"And hey, cool effects," O'Neill put in.
John stiffened. "Yes, sir. The point is, I'm not sure if I'm from an alternate reality or not."
"But McKay's usually right, huh?"
John glanced at McKay, who had his chin up as if he expected ridicule. "He's brilliant, sir, and he comes through in a pinch. Based on my experience, there's no one I'd trust more."
McKay gaped as if no one had ever expressed faith in him before. Then he went thoughtful. With two sentences, John had apparently gone from probable axe murderer to okay guy in McKay's mind.
O'Neill cleared his throat. "Yeah, about your experience . . . What do you know about Atlantis?"
"Well, in my, uh, reality, or history, or whatever, I'm the ranking military officer on the Atlantis expedition."
"Huh." O'Neill looked him up and down assessingly.
"I was included on the expedition because I have the Ancient gene. Almost as strong as yours, sir."
O'Neill's pleasant, slightly goofy expression went blank.
"McKay was there, too. He's the chief scientist on the expedition. My version of it, anyway."
McKay sighed. "I was supposed to be, but --" He broke off at a shake of the head from O'Neill.
"We went to investigate an Ancient outpost and we found something that McKay said looked like -- what did he call it? -- a database interface? Except he said it also gave off energy like a quantum mirror. I got too close to it, and next thing I know I'm in California and no one at the SGC has ever heard of me."
The general stared long enough to make John uncomfortable, and McKay started to fidget. Then O'Neill sighed and rubbed at his forehead. "I hate this weird shit," he complained. "All right. McKay, take him to the infirmary and get him tested. Get the whole story from him and figure out if it makes sense. You --" He pointed at John. "There'll be a guard on you, so don't try anything funny. Once the tests are done, come to the briefing room and explain it to me in small words. Well? What are you waiting for, go, go!"
-----
After what must have been a whirlwind tour of the spectacular views of Atlantis, Sheppard ended up lounging in the lab along with Teyla and Ronon.
Rodney tried to ignore their quiet conversation, snapping at Radek, "No no, we need the subspace data trace from the Ancient scanner at the moment it grabbed the Colonel's head."
"Rodney, you were not aiming scanner at the device then."
"It's subspace, non-directional! Do I have to explain everything?" Rodney grabbed for the scanner, but Radek pulled it away.
"So," Sheppard was saying in a low voice, "I'm the commander of this base?"
"Dr. Weir is leader of the expedition," Teyla corrected. "Colonel Sheppard commands the military personnel."
Rodney pointed at the data flowing across the screen. "Yes, that one! But further forward. Not that far, go back! Okay, slowly now . . ."
"I guess three years can make a hell of a difference," Sheppard went on. "How did I -- he get this command?"
"He shot his commanding officer," Ronon rumbled.
"Whoa! Wait, this isn't the universe with the beards, is it?" Sheppard's voice rose sharply.
Rodney jumped and twisted to glare at the interruption.
"Beards?" Teyla said doubtfully. "Dr. McKay once made a similar reference, but I did not understand it."
Rodney turned his eyes back to the large hanging screen. "There! Right there. Now increase the scale on the display. See that?"
"Butterfly signature," Radek breathed.
"Exactly. Four-fold symmetry. Two axes of reflection!"
In the background, Sheppard was telling Teyla and Ronon about Star Trek. "So in one episode there's this alternate universe where everyone -- well actually, just one or two people -- they have these wicked-looking beards, see? And they're all mean and evil, just looking out for themselves, always plotting and double-crossing each other, and they kill their leaders to get promoted. That sort of thing."
"Oh please!" Rodney snapped. "If we were evil we'd be taking advantage of you, or -- or using you to get an advantage over someone else, instead of wracking my brains trying to figure out how to get you home!"
Sheppard pouted sheepishly. "I was just asking. Ronon said --"
"It was not like that," Teyla replied, with a dark look at Ronon. "Colonel Sumner was captured and . . . tortured. He was fatally injured. Major Sheppard shot him as an act of mercy to end his pain."
"Rodney. Rodney. What does butterfly reflection tell us in this context?" Radek was asking.
Rodney huffed impatiently. "It tells us the transference was two-way. Look, Carson said the brainwaves showed the presence of only one consciousness. And we know it isn't the Colonel's consciousness."
Teyla continued, "We were not in contact with your planet at the time, so Major Sheppard took command. Later, when contact with Earth was re-established, he was promoted to Lieutenant Colonel so that he could continue doing the same job."
"So you look for the subspace reflection," Radek mused. "And the signature tells us Colonel Sheppard has gone to the same universe where this other Sheppard came from."
Rodney snapped a finger at him. "Precisely! That's where we have to start looking."
Radek went to the whiteboard. "So this double transference, it implies an inversion of the diacritic matrix --"
"No, not just an inversion! We're dealing with two separate dimensions here. It has to be a cross product of the two diacritic tensors . . . " Rodney snatched the marker away and started writing furiously.
In the corner, Sheppard was looking at Ronon suspiciously. "So, how long have you had that goatee?"
-----
"Yeah, it looked a lot like that," said John, nodding at the display McKay had put up on a monitor in the briefing room. "The colors were different, and the surface was, um, sort of 3-D looking, but it was basically like that."
Standing at the foot of the table, McKay turned to the others in the room: General O'Neill, Dr. Jackson, and Colonel Carter, whom John had met but never really spoken to. Teal'c was apparently off-world and Mitchell was recovering from their last mission. Carter looked like she could have used some more rest as well, but she was focused intently on what McKay was saying. Jackson, nursing a mug of coffee, seemed as alert as when he had taken John by surprise that morning.
McKay was wrapping up his explanation. "From Colonel Sheppard's description, the frame extruded and grabbed his head, and a bright light flashed in his eyes."
"Sounds familiar," said O'Neill.
"As far as it goes, yes. But apparently Colonel Sheppard didn't get the Ancient database downloaded into his brain."
"You sure?" O'Neill turned to John. "How long ago was this?"
"Two days. Almost." It seemed less to John, who had grown accustomed to the twenty-eight hour days on Atlantis.
"So maybe the crazy talk just hasn't started yet." O'Neill looked around the room. "I mean, you said he has that Ancient gene, so why wouldn't it work the same on him as it did on me? Takes a few days."
Jackson spoke up. "Well, but didn't the, uh, the increased brain activity show up even before you started speaking Ancient, Jack?"
"Daniel's right, sir," Carter put in. "From the rate of increase you experienced, the change in neural activity should be detectable as early as one day after the exposure." She turned to McKay. "Did they do a PET scan?"
"Of course, and an MRI and EEG. All perfectly normal. So I'm thinking this device, although similar, had a different purpose."
John frowned. "What about what you said -- I mean, what my Rodney said -- about it being like a quantum mirror?"
McKay snapped his fingers and pointed at John. "That's the key. From your description of the scanner my, uh, counterpart was looking at, he was probably seeing a subspace echo from the device."
"Right!" Carter leaned forward. "Quantum mirrors reflect subspace signals, only with --"
"With a characteristic phase offset, yes." McKay sat at the table with a triumphant smile, not seeming to notice that Carter was annoyed by his interruption. "It's very distinctive if you've seen it before."
"So what does all this mean?" O'Neill demanded. "It's like a quantum mirror but it isn't? It's like an Ancient brain-scrambler but not really?"
McKay slumped a little. "Without actually seeing the device or some scan data, all we have to go on are the effects, really."
"And the effect is that it transferred Colonel Sheppard's consciousness, but not his body, to another universe," Carter mused.
"Another planet, in another galaxy, in another universe," John pointed out. "And it all happened in the blink of an eye."
"The location shift would be automatic," McKay said dismissively. "It's the quantum singularity -- the shift in dimensions -- which takes all the energy. And even that is less than you'd think, with the proper tuning."
"And you think the choice of which reality to transfer to was based on a stray thought about surfing?" Carter asked.
John shrugged. "It was on my mind, just a little before the thing grabbed my head."
McKay added, "And he's already confirmed that his universe is very similar to this one. Proximity requires less energy."
Carter nodded thoughtfully.
"Maybe this is a dumb question," said Jackson slowly, "but what happened to the John Sheppard from this world, when Colonel Sheppard suddenly got transferred into his body?"
"I was wondering the same thing," said O'Neill brightly, chin propped on fist.
"Yes yes, we thought of that already and checked his EEG. The brain waves appear to show only one consciousness present," McKay said.
"Would it show up in the brain waves?" Carter asked. "If the two Sheppards are nearly identical, they could have the same pattern."
"I don't feel like there's anyone else in here," John volunteered. "Not like when McKay was sharing his brain with --"
"What?" McKay demanded.
"Never mind. Long story. Anyway, I didn't recognize this guy's apartment or car or anything. I haven't had any blackouts since I got here. I think I'm just me. In a body that's mostly like mine, but not exactly."
"Sharing my brain with what?" McKay hissed at him.
Carter turned to McKay. "So you think the transference was two-way?"
"Huh?" McKay dragged his attention back. "Oh. Yes. Well, if I could see a subspace scan of the device I'd know for sure. It was something we had considered when the quantum mirror was first found. Why shouldn't the transference go both ways? It would solve the problem of entropic cascade failure and balance the mass conservation equations better."
"Wait, how would that work?" said Jackson. "Unless the person in the other universe was touching the mirror at the same time as the person in this universe."
"It doesn't work, for exactly that reason. If the Daniel Jackson in universe A touches the mirror and transfers to universe B, the mirror can't instantaneously summon Daniel Jackson from wherever he is in universe B in order to transfer him to universe A. The energy cost would be prohibitive."
"Could be messy, too, if Daniel B is already dead and buried," said Jackson mildly.
"Can I just say, eww!" said O'Neill.
"But if the transference involves just consciousness, not bodies --" Carter began.
"The energy cost is less, and location isn't a factor," McKay finished, again missing her wince at the interruption. "In fact, since it conserves mass -- well, energy in this case -- and prevents entropic cascade, swapping two consciousnesses could turn out to be easier than transferring just one."
"Are you sure?" Carter asked. "The energy required just to violate the uncertainty principle twice instead of once --"
"But see, this way you can just take the cross product of the two --"
"Enough already!" said O'Neill. "Do the math later. It sounds like you know what probably happened, right? Colonel Sheppard is here in the wrong place, wrong body and so on, and Mr. Sheppard who belongs here is now there?"
McKay opened his mouth, but Carter cut him off with "Yes, sir, we think so."
"So, what do we do about it?"
"Can we send him back where he belongs?" Jackson asked.
McKay and Carter looked at each other.
"Well," Carter ventured, "since the original transference only required one of them to be in contact with the device --"
"It should only require one of them to change back, of course!" McKay finished.
"Unless it has a block to prevent reversals, like Machello's body-switching machine," Jackson pointed out.
"No no, the Ancients didn't operate like that," said McKay.
"You think they didn't," Carter retorted.
"Okay, so wait," said John, rubbing circles at his temples. "The device is in the Pegasus galaxy -- at least it was in my universe, and probably is in this one. So you're saying I need to travel back to Pegasus to get to the device again in order to get home?"
McKay left off glaring at Carter. "Nonononono, it's much simpler than that. My counterpart in your universe is going to reach the same conclusion we did and take your counterpart back to the device. All you need to do is wait."
"Then why hasn't it happened yet?" John asked. "You just found out about it this morning and figured it out in a few hours. They've known about it for two days. How long am I supposed to wait?"
-----
"So you're saying if Mr. Sheppard goes back to the outpost and activates the device again, the switch will be undone?" Elizabeth asked.
Sheppard leaned a shoulder on the door to her office and frowned as he listened.
Rodney shook his head. "No no, it's not that simple. We have no idea how the device determined which universe to switch with in the first place. There was no control mechanism like we had with the quantum mirror in Area 51."
"We do know it was a universe very similar to our own --" said Radek.
"Yes, it seems to have split off just about three years ago, which is very recent in cosmic terms," Rodney agreed.
"But this still leaves an incredible number of possible universes." Radek pushed his glasses up his nose.
"We need to figure out how to control which universe we're swapping with, or we'll just end up with a completely new Sheppard and send this Sheppard to some other place that still isn't his home."
"That doesn't sound good," Sheppard drawled.
"And there were no instructions aside from this inscription?" Elizabeth turned to her laptop, which was displaying an image from Rodney's scans. She traced the semicircle of Ancient symbols around the device. "'Learn what might have been, worlds apart,'" she read.
"Not so helpful," Sheppard commented.
"Right, that's what the device does," said Rodney, "but unfortunately there's nothing there about how to undo it without making things even worse."
Radek added, "It's possible that there were once controls and perhaps instructions in the outer room --"
"But that room was vandalized," Rodney finished.
Elizabeth pursed her lips. "A lot of Ancient technology requires a mental component for operation. Could that be the case here?"
"There probably is a mental component, but something this complex requires more for full control," said Rodney.
"And we cannot test. If we take Mr. Sheppard to the outpost and switch him with wrong universe --"
"That would make the problem infinitely more complicated to untangle. We need to be careful here, or we might never get our Colonel Sheppard back."
Elizabeth sighed. "Understood. Take as much time as you need to be sure. Would it help to go back and examine the device again?"
Rodney shook his head. "I don't think so. I've done all the scans that can be done, short of triggering it again."
"Which we cannot do," Radek added.
Rodney cocked his head. "Unless . . . you don't suppose it would trigger for one of Carson's gene therapy mice?"
"A mouse?" said Sheppard. "Even if it worked, how could you tell if you got the wrong one back?"
Rodney grimaced. "Yes, good point."
Radek added, "And we would run the risk of overwriting memory buffer of last transfer."
"The memory buffer!" Rodney exclaimed. "If it's intact, and we can access the data without destroying it --"
"Then we could develop a test for correct universe to transfer to --" Radek continued.
"-- And maybe build our own control device!"
Elizabeth looked blankly between the two of them. "Well, good. It sounds like you have a plan. Now figure out if it will work. Tell me if there's anything you need."
"Yes yes, of course." Rodney waved absently at her as he and Radek left her office, still finishing each other's sentences.
Part Three
Title: Cross Product, Part 2
Author: Quasar
Rating: PG-13 for this part, NC-17 eventually
Pairing: McKay/Sheppard
Spoilers: specific references up to Duet, vague ones up to Allies
Date written: July 2006
Length: ~5,000 words for this part
Summary: McKay interrupts Carter and brain-melds with Zelenka.
Link to Part One
A day and a half later, John was in Colorado Springs, feeling punchy from too much caffeine and not enough sleep. The little Mustang, despite its battered appearance, had performed like a dream, and he had lost some of his tension as the miles slipped by. Now he was remembering everything he had to worry about. Was he about to face down a real -- and really angry -- general, or was he about to blow this fake world out of the water?
He'd stopped at a little coffeehouse just at the edge of town on the road to the Cheyenne Mountain complex. He was contemplating his strategy over capuccino and a slice of spinach-artichoke quiche when Dr. Daniel Jackson walked in. John hadn't gotten to know the man well in Antarctica, but he had lumped him in the same class as McKay: brilliant, excitable, and near-impossible to draw away from his work. John was definitely wishing he had Rodney here to untangle this bizarre situation. But given their similarities in disposition, maybe Jackson was someone who would listen with an open mind.
He watched as the archaeologist ordered a large double espresso and sat down with a huge leather-bound tome balanced on his knees. Standing and unconsciously tugging at his rumpled shirt, John considered the best way to approach the man. He was just crossing past the doorway when someone entering bumped into him.
It was McKay.
John's jaw dropped. "Rodney! You're here too? Thank God, I could use the help." He started to clasp McKay's upper arms, but the scientist was pulling back and lifting his elbows, and somehow John ended up grabbing him by the ribs instead. It seemed only natural to slide forward and give him a hug.
Natural to John, but apparently not to Rodney, who stiffened and pushed him away with an appalled look.
"How did you get here?" John asked. "Do you know how to get back?"
"Back?" said McKay weakly, his eyes flashing over Sheppard's shoulder.
"I take it this place isn't real, then?" John blew out a breath in relief. "That's what I figured, but I wasn't sure. I'm glad to see you -- I thought I was all alone here."
"Um . . ."
Hollow-headed with exhaustion, John didn't notice that he was doing a lot more than his usual share of the talking. "What did you do, stick your head in that device to come after me, after all the warning me about how dangerous it was? I just hope you've got some kind of back door ready to let us out of here, because I haven't had any luck thinking myself out so far."
"Hi, Rodney, is this a friend of yours?"
John turned to find Jackson at his elbow. The man seemed very mild-mannered, blinking at the two of them pleasantly, but something about his stance raised John's hackles. He automatically started to place himself between McKay and the threat. "I work with Rodney," he answered, and held out a hand. "John Sheppard."
Jackson smiled but didn't shake. "Daniel Jackson."
"Yes, I know --"
"Daniel, I've never seen this man before in my life!" McKay said, in tones of near-panic.
John's head whipped around. "Wait, what? I thought you entered the simulation to help me out!"
"Simulation?" Jackson asked quickly.
John stepped back to get both of them in view, but Jackson shifted to flank him without seeming to do it deliberately. John realized the faint threat he sensed was directed at him, and he suddenly recalled that the quiet archaeologist effectively had more combat experience than many veteran Marines.
Except that this was just a virtual representation of Daniel Jackson -- wasn't it?
"What are you talking about? What simulation?" McKay demanded.
"Well, this, uh, all of this." John waved vaguely at the cafe. "This isn't real, is it? It can't be real." After all, Rodney had appeared right after he wished for him.
"Did you forget your little pills this morning? Of course it's real!"
Jackson squinted and rubbed his nose. "I've always found it simplest to assume things are real until I see evidence to the contrary."
John shook his head in confusion. "But it doesn't make any sense. If this is really Earth, why is everything different? And how did I get here from Pegasus?"
"If this is Earth?" Jackson repeated, at the same moment that McKay said, "Pegasus?"
"Yeah, you know, a galaxy far, far away? Home of Atlantis?"
There was a moment of stunned silence, and John wondered if he shouldn't have mentioned the Ancient city. But if the aliens creating the virtual reality wanted to know about Atlantis, that could be the key to cracking their illusion.
Assuming it was an illusion. He still wasn't sure about that.
McKay looked around the mostly-empty cafe before hissing, "How do you know about --"
"Atlantis is, is a myth," Jackson interrupted.
"Yes, right, of course, a myth," McKay said quickly. "Whereas this, here, Earth, is real. Are the hair gel fumes making you confuse fantasy with reality?"
"No. No, this doesn't make sense." John stumbled back until he hit a chair and sat down. "If this is real . . . if this is real . . . but it's all wrong. Damn, why is it wrong? My head hurts." He rubbed at his temples.
"What precisely do you think is wrong with this, um, this world?" Jackson asked quietly.
"History is wrong. I'm wrong -- I'm not supposed to be on this planet at all. And you don't recognize me, and McKay acts like I'm an axe murderer or something -- it's all just wrong!"
Jackson squinted at McKay. "You know, this seems sort of familiar."
McKay nodded. "It almost sounds like he's describing --"
"-- an alternate reality," they finished in unison.
"A what?" John asked, but at that moment the cafe door opened.
A couple of uniformed men walked in, nodded to Jackson and took up positions looming over John with their hands poised over their sidearms. "I'll have to ask you to come with us, sir," the older one said.
John felt strangely as if he'd just screwed up a first contact mission.
-----
"So, let me get this straight." Seated at the conference room table, Sheppard looked between Rodney and Elizabeth. "These . . . Ancient aliens you're talking about invented some gates for traveling between planets."
"Stargates, yes," said Elizabeth.
"And they left one on Earth."
"Two, actually," Rodney said, garnering annoyed looks from the others. "But we don't need to go into the details just now."
"And the Air Force discovered this gate thing and started sending expeditions to other planets."
"Not just the Air Force . . . well, yes, basically." Rodney subsided under combined glares.
"And we're on another planet right now."
"That's right." Elizabeth smiled at him.
"You might notice the gravity is just a little lower than Earth's, by about three percent."
"He doesn't need to know every detail at once, Rodney," Carson protested.
"Come on, he's a pilot! He notices things like this. It's the simplest way to prove that what we said is true." Rodney turned back to Sheppard. "The other planet, with all the sand, that one had a gravity almost fifteen percent higher than Earth's."
Sheppard blinked. "I just thought my vest was loaded down."
"If you had dropped something, or tripped, you would have noticed that the acceleration --"
"Enough, Rodney," said Elizabeth. "I think he believes we're not on Earth."
"We're on -- in -- Atlantis," said Sheppard, returning to his recap.
"Yes."
"A floating city built by those same aliens."
"Actually, they were physically indistinguishable from humans, with differences primarily noticeable at the genetic level," Carson began, then noticed that Rodney and Elizabeth were glaring at him now. "But, yes, not originally from Earth."
Sheppard was distracted. "Wait, why would they look like humans? Is there some reason for that?"
"Well, technically we're descended from them," Carson said. "So are the races of the Pegasus Galaxy, like Teyla and Ronon here."
Sheppard turned to look at the other two members of the team. "You guys are aliens?"
"We are not from your Earth," said Teyla gravely.
"Whoa," said Sheppard. Then he looked back at Rodney. "But none of this explains why I'm here."
"Well, you -- or rather, our Colonel Sheppard -- is part of the Atlantis expedition. He has a gene which lets him interface more efficiently with some of the Ancient technology. We found a device on that desert planet, and Sheppard activated it by accident, and . . . it switched you into his place. I'm still working out the details of how that happened, and we need to understand before we can try to do anything about it." Rodney frowned and stood up. "In fact, I should be getting back to my lab. Zelenka must have finished going over those scans by now."
"I'll want an update before dinner," Elizabeth called after him as he headed for the door, and he waved a hand in acknowledgment. Behind him, she said. "Teyla, Ronon -- could you show Mr. Sheppard around, please? Make sure he doesn't get lost?"
-----
John was locked in a mostly bare room under Cheyenne Mountain. All his personal effects had been removed and he was wearing fatigues with no insignia, but on request he'd been given a pad of paper and a soft-tipped pen. Now he was sitting on the end of the bunk with the notepad on his lap. On the top page he had drawn two columns: REAL and NOT REAL.
In the NOT REAL column he had written "wrong history," "wrong body," "wrong planet," "instantaneous intergalactic transport?" "thought about surfing -- ended up surfing," and "wished for RM -- RM appeared." In the REAL column he had written "feels real," and "can't control it." He put a question mark after the latter, with arrows to the surfing and RM items in the opposite column. Frowning, he added "RM says it's real." Then he crossed that out and wrote "all Cretans are liars" underneath.
With a muttered curse he ripped off the top page and headed the next CRAZY and NOT CRAZY. He stared at the paper for several minutes before scribbling "see page 1" and dropping the notepad to his side. He flopped back on the bed and lay with one arm across his eyes.
He heard his door guard greet someone and sat up just as the door opened. General Jack O'Neill came in and eyed John curiously. He stood quickly and saluted.
O'Neill waved a hand vaguely. "Colonel Sheppard, I presume?"
John blinked. "That's right."
"And from that phone call I guess you know who I am?"
"Yes, sir."
"McKay here thinks you're from some kind of parallel universe." O'Neill glanced at the door where McKay was hovering uncertainly. "Oh, come in and shut the door!" he snapped.
McKay came in, but kept the bunk positioned between himself and John.
"Well?" said O'Neill.
"Uh . . . Rodney is usually right, sir. But there's a lot that doesn't make sense."
"You think? So what else is new?"
McKay retrieved the discarded page of paper from the floor. "Wrong body?" he read. "Instantaneous intergalactic transport?"
"Yeah," said John. "Those are the parts that don't seem to fit with other reports I've seen about alternate realities."
"And based just on that, you decided this was some kind of virtual environment?" McKay's tone implied that would be a monumental feat of stupidity.
John shrugged, relaxing under the familiar weight of McKay's sarcasm. "Well, at least I've encountered those before. And there were some coincidences that made me wonder. You know, like the black cat in the Matrix."
"Oh, please! That movie had to be the most appalling exercise in illogic I've ever seen."
"It wasn't that bad," John protested.
"Human beings -- drugged humans with atrophied muscles -- as energy sources? Their nutrition and maintenance would require far more energy than the minimal heat return. It's a basic principle of thermodynamics!"
"Okay, so the premise had some flaws, but the movie was internally consistent. Mostly."
"And hey, cool effects," O'Neill put in.
John stiffened. "Yes, sir. The point is, I'm not sure if I'm from an alternate reality or not."
"But McKay's usually right, huh?"
John glanced at McKay, who had his chin up as if he expected ridicule. "He's brilliant, sir, and he comes through in a pinch. Based on my experience, there's no one I'd trust more."
McKay gaped as if no one had ever expressed faith in him before. Then he went thoughtful. With two sentences, John had apparently gone from probable axe murderer to okay guy in McKay's mind.
O'Neill cleared his throat. "Yeah, about your experience . . . What do you know about Atlantis?"
"Well, in my, uh, reality, or history, or whatever, I'm the ranking military officer on the Atlantis expedition."
"Huh." O'Neill looked him up and down assessingly.
"I was included on the expedition because I have the Ancient gene. Almost as strong as yours, sir."
O'Neill's pleasant, slightly goofy expression went blank.
"McKay was there, too. He's the chief scientist on the expedition. My version of it, anyway."
McKay sighed. "I was supposed to be, but --" He broke off at a shake of the head from O'Neill.
"We went to investigate an Ancient outpost and we found something that McKay said looked like -- what did he call it? -- a database interface? Except he said it also gave off energy like a quantum mirror. I got too close to it, and next thing I know I'm in California and no one at the SGC has ever heard of me."
The general stared long enough to make John uncomfortable, and McKay started to fidget. Then O'Neill sighed and rubbed at his forehead. "I hate this weird shit," he complained. "All right. McKay, take him to the infirmary and get him tested. Get the whole story from him and figure out if it makes sense. You --" He pointed at John. "There'll be a guard on you, so don't try anything funny. Once the tests are done, come to the briefing room and explain it to me in small words. Well? What are you waiting for, go, go!"
-----
After what must have been a whirlwind tour of the spectacular views of Atlantis, Sheppard ended up lounging in the lab along with Teyla and Ronon.
Rodney tried to ignore their quiet conversation, snapping at Radek, "No no, we need the subspace data trace from the Ancient scanner at the moment it grabbed the Colonel's head."
"Rodney, you were not aiming scanner at the device then."
"It's subspace, non-directional! Do I have to explain everything?" Rodney grabbed for the scanner, but Radek pulled it away.
"So," Sheppard was saying in a low voice, "I'm the commander of this base?"
"Dr. Weir is leader of the expedition," Teyla corrected. "Colonel Sheppard commands the military personnel."
Rodney pointed at the data flowing across the screen. "Yes, that one! But further forward. Not that far, go back! Okay, slowly now . . ."
"I guess three years can make a hell of a difference," Sheppard went on. "How did I -- he get this command?"
"He shot his commanding officer," Ronon rumbled.
"Whoa! Wait, this isn't the universe with the beards, is it?" Sheppard's voice rose sharply.
Rodney jumped and twisted to glare at the interruption.
"Beards?" Teyla said doubtfully. "Dr. McKay once made a similar reference, but I did not understand it."
Rodney turned his eyes back to the large hanging screen. "There! Right there. Now increase the scale on the display. See that?"
"Butterfly signature," Radek breathed.
"Exactly. Four-fold symmetry. Two axes of reflection!"
In the background, Sheppard was telling Teyla and Ronon about Star Trek. "So in one episode there's this alternate universe where everyone -- well actually, just one or two people -- they have these wicked-looking beards, see? And they're all mean and evil, just looking out for themselves, always plotting and double-crossing each other, and they kill their leaders to get promoted. That sort of thing."
"Oh please!" Rodney snapped. "If we were evil we'd be taking advantage of you, or -- or using you to get an advantage over someone else, instead of wracking my brains trying to figure out how to get you home!"
Sheppard pouted sheepishly. "I was just asking. Ronon said --"
"It was not like that," Teyla replied, with a dark look at Ronon. "Colonel Sumner was captured and . . . tortured. He was fatally injured. Major Sheppard shot him as an act of mercy to end his pain."
"Rodney. Rodney. What does butterfly reflection tell us in this context?" Radek was asking.
Rodney huffed impatiently. "It tells us the transference was two-way. Look, Carson said the brainwaves showed the presence of only one consciousness. And we know it isn't the Colonel's consciousness."
Teyla continued, "We were not in contact with your planet at the time, so Major Sheppard took command. Later, when contact with Earth was re-established, he was promoted to Lieutenant Colonel so that he could continue doing the same job."
"So you look for the subspace reflection," Radek mused. "And the signature tells us Colonel Sheppard has gone to the same universe where this other Sheppard came from."
Rodney snapped a finger at him. "Precisely! That's where we have to start looking."
Radek went to the whiteboard. "So this double transference, it implies an inversion of the diacritic matrix --"
"No, not just an inversion! We're dealing with two separate dimensions here. It has to be a cross product of the two diacritic tensors . . . " Rodney snatched the marker away and started writing furiously.
In the corner, Sheppard was looking at Ronon suspiciously. "So, how long have you had that goatee?"
-----
"Yeah, it looked a lot like that," said John, nodding at the display McKay had put up on a monitor in the briefing room. "The colors were different, and the surface was, um, sort of 3-D looking, but it was basically like that."
Standing at the foot of the table, McKay turned to the others in the room: General O'Neill, Dr. Jackson, and Colonel Carter, whom John had met but never really spoken to. Teal'c was apparently off-world and Mitchell was recovering from their last mission. Carter looked like she could have used some more rest as well, but she was focused intently on what McKay was saying. Jackson, nursing a mug of coffee, seemed as alert as when he had taken John by surprise that morning.
McKay was wrapping up his explanation. "From Colonel Sheppard's description, the frame extruded and grabbed his head, and a bright light flashed in his eyes."
"Sounds familiar," said O'Neill.
"As far as it goes, yes. But apparently Colonel Sheppard didn't get the Ancient database downloaded into his brain."
"You sure?" O'Neill turned to John. "How long ago was this?"
"Two days. Almost." It seemed less to John, who had grown accustomed to the twenty-eight hour days on Atlantis.
"So maybe the crazy talk just hasn't started yet." O'Neill looked around the room. "I mean, you said he has that Ancient gene, so why wouldn't it work the same on him as it did on me? Takes a few days."
Jackson spoke up. "Well, but didn't the, uh, the increased brain activity show up even before you started speaking Ancient, Jack?"
"Daniel's right, sir," Carter put in. "From the rate of increase you experienced, the change in neural activity should be detectable as early as one day after the exposure." She turned to McKay. "Did they do a PET scan?"
"Of course, and an MRI and EEG. All perfectly normal. So I'm thinking this device, although similar, had a different purpose."
John frowned. "What about what you said -- I mean, what my Rodney said -- about it being like a quantum mirror?"
McKay snapped his fingers and pointed at John. "That's the key. From your description of the scanner my, uh, counterpart was looking at, he was probably seeing a subspace echo from the device."
"Right!" Carter leaned forward. "Quantum mirrors reflect subspace signals, only with --"
"With a characteristic phase offset, yes." McKay sat at the table with a triumphant smile, not seeming to notice that Carter was annoyed by his interruption. "It's very distinctive if you've seen it before."
"So what does all this mean?" O'Neill demanded. "It's like a quantum mirror but it isn't? It's like an Ancient brain-scrambler but not really?"
McKay slumped a little. "Without actually seeing the device or some scan data, all we have to go on are the effects, really."
"And the effect is that it transferred Colonel Sheppard's consciousness, but not his body, to another universe," Carter mused.
"Another planet, in another galaxy, in another universe," John pointed out. "And it all happened in the blink of an eye."
"The location shift would be automatic," McKay said dismissively. "It's the quantum singularity -- the shift in dimensions -- which takes all the energy. And even that is less than you'd think, with the proper tuning."
"And you think the choice of which reality to transfer to was based on a stray thought about surfing?" Carter asked.
John shrugged. "It was on my mind, just a little before the thing grabbed my head."
McKay added, "And he's already confirmed that his universe is very similar to this one. Proximity requires less energy."
Carter nodded thoughtfully.
"Maybe this is a dumb question," said Jackson slowly, "but what happened to the John Sheppard from this world, when Colonel Sheppard suddenly got transferred into his body?"
"I was wondering the same thing," said O'Neill brightly, chin propped on fist.
"Yes yes, we thought of that already and checked his EEG. The brain waves appear to show only one consciousness present," McKay said.
"Would it show up in the brain waves?" Carter asked. "If the two Sheppards are nearly identical, they could have the same pattern."
"I don't feel like there's anyone else in here," John volunteered. "Not like when McKay was sharing his brain with --"
"What?" McKay demanded.
"Never mind. Long story. Anyway, I didn't recognize this guy's apartment or car or anything. I haven't had any blackouts since I got here. I think I'm just me. In a body that's mostly like mine, but not exactly."
"Sharing my brain with what?" McKay hissed at him.
Carter turned to McKay. "So you think the transference was two-way?"
"Huh?" McKay dragged his attention back. "Oh. Yes. Well, if I could see a subspace scan of the device I'd know for sure. It was something we had considered when the quantum mirror was first found. Why shouldn't the transference go both ways? It would solve the problem of entropic cascade failure and balance the mass conservation equations better."
"Wait, how would that work?" said Jackson. "Unless the person in the other universe was touching the mirror at the same time as the person in this universe."
"It doesn't work, for exactly that reason. If the Daniel Jackson in universe A touches the mirror and transfers to universe B, the mirror can't instantaneously summon Daniel Jackson from wherever he is in universe B in order to transfer him to universe A. The energy cost would be prohibitive."
"Could be messy, too, if Daniel B is already dead and buried," said Jackson mildly.
"Can I just say, eww!" said O'Neill.
"But if the transference involves just consciousness, not bodies --" Carter began.
"The energy cost is less, and location isn't a factor," McKay finished, again missing her wince at the interruption. "In fact, since it conserves mass -- well, energy in this case -- and prevents entropic cascade, swapping two consciousnesses could turn out to be easier than transferring just one."
"Are you sure?" Carter asked. "The energy required just to violate the uncertainty principle twice instead of once --"
"But see, this way you can just take the cross product of the two --"
"Enough already!" said O'Neill. "Do the math later. It sounds like you know what probably happened, right? Colonel Sheppard is here in the wrong place, wrong body and so on, and Mr. Sheppard who belongs here is now there?"
McKay opened his mouth, but Carter cut him off with "Yes, sir, we think so."
"So, what do we do about it?"
"Can we send him back where he belongs?" Jackson asked.
McKay and Carter looked at each other.
"Well," Carter ventured, "since the original transference only required one of them to be in contact with the device --"
"It should only require one of them to change back, of course!" McKay finished.
"Unless it has a block to prevent reversals, like Machello's body-switching machine," Jackson pointed out.
"No no, the Ancients didn't operate like that," said McKay.
"You think they didn't," Carter retorted.
"Okay, so wait," said John, rubbing circles at his temples. "The device is in the Pegasus galaxy -- at least it was in my universe, and probably is in this one. So you're saying I need to travel back to Pegasus to get to the device again in order to get home?"
McKay left off glaring at Carter. "Nonononono, it's much simpler than that. My counterpart in your universe is going to reach the same conclusion we did and take your counterpart back to the device. All you need to do is wait."
"Then why hasn't it happened yet?" John asked. "You just found out about it this morning and figured it out in a few hours. They've known about it for two days. How long am I supposed to wait?"
-----
"So you're saying if Mr. Sheppard goes back to the outpost and activates the device again, the switch will be undone?" Elizabeth asked.
Sheppard leaned a shoulder on the door to her office and frowned as he listened.
Rodney shook his head. "No no, it's not that simple. We have no idea how the device determined which universe to switch with in the first place. There was no control mechanism like we had with the quantum mirror in Area 51."
"We do know it was a universe very similar to our own --" said Radek.
"Yes, it seems to have split off just about three years ago, which is very recent in cosmic terms," Rodney agreed.
"But this still leaves an incredible number of possible universes." Radek pushed his glasses up his nose.
"We need to figure out how to control which universe we're swapping with, or we'll just end up with a completely new Sheppard and send this Sheppard to some other place that still isn't his home."
"That doesn't sound good," Sheppard drawled.
"And there were no instructions aside from this inscription?" Elizabeth turned to her laptop, which was displaying an image from Rodney's scans. She traced the semicircle of Ancient symbols around the device. "'Learn what might have been, worlds apart,'" she read.
"Not so helpful," Sheppard commented.
"Right, that's what the device does," said Rodney, "but unfortunately there's nothing there about how to undo it without making things even worse."
Radek added, "It's possible that there were once controls and perhaps instructions in the outer room --"
"But that room was vandalized," Rodney finished.
Elizabeth pursed her lips. "A lot of Ancient technology requires a mental component for operation. Could that be the case here?"
"There probably is a mental component, but something this complex requires more for full control," said Rodney.
"And we cannot test. If we take Mr. Sheppard to the outpost and switch him with wrong universe --"
"That would make the problem infinitely more complicated to untangle. We need to be careful here, or we might never get our Colonel Sheppard back."
Elizabeth sighed. "Understood. Take as much time as you need to be sure. Would it help to go back and examine the device again?"
Rodney shook his head. "I don't think so. I've done all the scans that can be done, short of triggering it again."
"Which we cannot do," Radek added.
Rodney cocked his head. "Unless . . . you don't suppose it would trigger for one of Carson's gene therapy mice?"
"A mouse?" said Sheppard. "Even if it worked, how could you tell if you got the wrong one back?"
Rodney grimaced. "Yes, good point."
Radek added, "And we would run the risk of overwriting memory buffer of last transfer."
"The memory buffer!" Rodney exclaimed. "If it's intact, and we can access the data without destroying it --"
"Then we could develop a test for correct universe to transfer to --" Radek continued.
"-- And maybe build our own control device!"
Elizabeth looked blankly between the two of them. "Well, good. It sounds like you have a plan. Now figure out if it will work. Tell me if there's anything you need."
"Yes yes, of course." Rodney waved absently at her as he and Radek left her office, still finishing each other's sentences.
Part Three