An internal monologue that must have happened during the plot of last night's Sherlock...
"It must be tonight. He knows too much. Despite our friendship, he has to die. The moor's the place to do it - use the gas to confuse him, then finish him off before he comes to his senses. Now what to wear. Hmm. Dark clothes are traditional for this sort of thing, but my wardrobe is full of suits and lab coats. Oh hang on, here are two dark t-shirts. Hmm. The plain black one, or the one with the logo and identifying detail of the secret research group that came up with the weapon I'm about to use to do a murder. Gosh, this is a real poser. This little voice in my head is telling me that the H.O.U.N.D. one is a bad idea, but the plain black one's just so...dull. Nothing for it, got to be the secret researcher one. I'm sure the nagging voice is nothing to worry about. In fact, I see no possible flaw in this plan."
And he would have gotten away with it too, if it wasn't for those meddling consulting detectives.