Hmm, an interesting take on the Sherlock Holmes/Dr. Watson story, set in a post-apoclyptic 2010, where the loss of 98% of Earth's population was wiped out in a single (unexplained) event. Only those who were inside in windowless rooms or underground survived the event, so nobody really knows what happened.
Holmes is outside in the remains of London, trying to find evidence to solve a pre-event crime - not that it's of any use/relevance, but Holmes' inquiring mind can't let it rest - when he stumbles across John Watson. This Watson is not a bumbling fool, but rather a traumatized yet extremely capable Army doctor trying to survive by himself.
Holmes eventually manages to persuade Watson to return with him to the Enclave, where the remains of the British government have gathered underground, including Holmes' brother, Mycroft, and Inspector Lestrade.
Without giving away the story, the reader soon realizes that most of the main characters from Conan Doyle's story appear here, so the crime side of things comes as no real surprise. But even knowing that Holmes and Watson will become more than a crime-fighting duo (because it is slash fiction), the way it happens, and the end is a surprise.
(I'm not saying anything else, but it wouldn't hurt to check which shelves I have added it to...)