This is what you need to know about Sarah Walker: She kicks ass.
Sarah comes from the TV show "Chuck," a comedy-action TV series that debuted on NBC in the fall of 2007 and is now returning for its second season. In it, a rogue CIA agent emails a file to his old college roommate, Chuck Bartowski, containing a top-secret government database known as "the Intersect." The Intersect is an encoded compilation of information used by national security agencies to track down terrorists and other threats to U.S. interests within the country. After Chuck runs the file, the information is embedded in his brain and can be accessed only when he "flashes" on specific targets.
The government is trying to replicate the information in the Intersect, but that's taking a while. In the meantime, two government agents, Sarah Walker of the CIA and John Casey of the NSA, are assigned to keep watch over the Intersect and, incidentally, Chuck. Sarah goes undercover as a fast food worker and Chuck's girlfriend; Casey takes a job at Buy More as his cover. Casey would as soon shoot Chuck as look at him for most of the first season (and is under orders to do so if the Intersect is ever recovered), but Chuck and Sarah quickly find a certain rapport.
It's hard to give too much background on Sarah because the show is told from Chuck's point of view, and Sarah has almost never broken cover to confide in Chuck. We know Sarah Walker is an alias, and that her real middle name is Lisa. She was recruited to the CIA right out of high school and went to Harvard before joining the Agency. (More background was given in last week's episode, but as it's unlikely to be relevant, I'm skipping it to avoid spoilers.)
Sarah's main personal conflict is between her job and her heart. Her job usually wins, but not without some clear cost to Sarah as she tries to be the consummate professional spy. She keeps her emotions on the inside and makes a point of not falling apart or revealing too much of herself, usually channeling any stress into workouts or target practice (and, occasionally, the odd bit of violence to any handy inanimate object). She'll be the person the mission needs her to be, and doesn't hesitate to take charge when that's what is called for. When nothing in particular is needed, she defaults to being business-like, quiet and wary. Sarah claims in the first episode that she's not funny, and that's mostly true. She may have a sense of humor -- she likes Chuck, after all -- but she's not one to make jokes. However, within her limits she's friendly to others.
As her profession would require, she's a fantastic liar -- as long as she doesn't care too much about the person she's talking to. In a conversation with someone she's close to, she tends to go quiet or change the subject rather than directly lying.
Physically, Sarah is tall -- 5' 10", according to her official spy dossier -- and thin but well-muscled, with blond hair falling past her shoulder blades and deep blue eyes. She is extremely pretty by conventional standards, though not at all vain beyond what's needed for her undercover work. While she'll wear whatever is needed to fit in on a mission, her off-duty default seems to be tank tops and jeans.
Sarah is a CIA-educated spy, expert in hand-to-hand combat, weapons, and disguise. She dances well, fights better, and can switch from dancing to fighting without messing up her dress. She can take down guys twice her size, even from a hospital bed. She's an excellent shot and will shoot a person without blinking, and normally wears a handgun in the small of her back or a knife strapped to her thigh. She's been trained to resist truth serums. She has no scruples about using her sexuality if it's what's needed on a mission, and has been educated in the art of seduction. She speaks several languages, including Russian, German, Polish and Spanish. A very smart woman, she's been trained to always be one step ahead of everyone in the room, and normally she is.
However, she is still a normal human, and no stronger, faster or more agile than any incredibly well-trained woman of her size could be. She can be bested in a fight if someone else is skilled enough and gets her off-guard.
Sarah is coming to Fandom just after the second season episode "Chuck vs. the Break-Up." At this point in canon, Sarah and Chuck have acknowledged they have real feelings for each other, but it's a mess because she won't date him while he's officially under her protection, and he claims he doesn't want to date a spy whose real name he doesn't even know anyhow. Meanwhile, efforts to rebuild the Intersect have been destroyed, so the government is back at square one in its efforts to return Chuck to his normal life.
To get Sarah to Fandom, I'm going to say her supervisor, General Beckman, is aware of Chuck and Sarah's budding relationship. Sarah was unable to bring down an enemy agent when taking a shot would have put Chuck in danger, which forced Casey to intercede. Because Sarah was also involved with her last partner, Beckman and other CIA officials have become concerned that she's regularly letting her emotions get the better of her.
They're taking her off the Intersect job and sending her to Fandom on an enforced sabbatical to watch for and recruit budding spies and, as a cover, run the comics store. (She let Chuck pick her cover job. Never again, she'll tell you.) Meanwhile, Chuck's case is being reassigned to an NPC agent.
As far as she'll be telling people in Fandom at first, she's a wannabe actress from L.A. who inherited the business from her brother. She won't be public initially about her CIA past, though anyone who sees her in a fight or in the gym is welcome to surmise that she has training. She eventually will break cover, either with law enforcement types or as part of efforts to get students to come work for the Agency.
She'll be in Fandom tomorrow or Wednesday, depending on when I get her entrance post ficced out, and will be hiring at the comics store. Poke me if your character is interested in a job.