What it says on the tin. (Including Follow-ups to: Maybe one of these days you can let the light in, and One Of Those Things, and Mrs and Mr Pond..)

“Eternity is really rather boring, John. Mortal life seemed as though it would be far more interesting.” Sherlock is actually the Devil, but he decided to live as a mortal because ruling Hell was boring.

And how things could have gone differently.

“Your first mistake,” John says smoothly, “was calling yourself Moriarty. It got my attention.” In which Jim is not, in fact, Moriarty.

John and Sherlock have something in common of which they are both unaware. They've both been holding back from starting a relationship with the other because of the one aspect of their lives they are *sure* they cannot share. Serial Killer AU.