The Final Problem

battledinosaur asked: I don't know if you've already answered this but I just re-watched The Fall and noticed something that I don't think was ever... resolved. in the text Sherlock sends to Moriarty, he says "P.S. got something of yours you might want back" or something like that. what do you think it is? at first I thought it was the "keycode" but that isn't something that, when one person has it, the other doesn't. they both "had it". what do you think it was?

I think it was the key code.

You’re right that since the (imaginary) key code turned out to be a binary sequence not stored in physical form, Sherlock couldn’t really have given it “back” to Jim.

But up until the roof scene, they had been acting like the key code was stored on some physical object (memory stick or whatever) and hidden in 221B.

Sherlock: Tell me what you want from me. Tell me!

Assassin: He left it at your flat.

Sherlock: Who?

Assassin: Moriarty.

Sherlock: What?

Assassin: The computer key code.

Sherlock: Of course. He’s selling it. The programme he used to break into the Tower. He planted it when he came around.

I think they had Sherlock go ahead and use that wording in his text playfully, because they didn’t want to ruin the surprise that was coming up for the viewers. (They had suggested the finger tap binary at that point, but not directly stated the secret.)