Missing a Heart

The Doctor's just lost Rose, Sherlock and John have finally admitted their feelings for each other, and Sam and Dean have just found some girl in the middle of the night who's wanted by the mafia. The Winchesters get a case which leads them to London, where Sherlock, John, Sherlock's niece, Sam, Dean, and the Doctor all cross paths. (Crap description I know, but I guarantee the story is a lot better.)