The Loss of Flesh and Soul , by deuxexmycroft [fanfiction]
"You're remarkable," Sherlock suddenly whispered, lips right against John's ear. His breath brushed flushed skin. "I think I'll eat your heart."
Description: Five years after John Watson puts the murderous Sherlock Holmes behind bars, a vicious copycat killer emerges. A reluctant John is pulled out of retirement to seek the expertise of the only man who can help, a man who has developed an unsettling obsession with John himself.
Crossover with Red Dragon/Silence of the Lambs [link]
Warnings: Psychopath!Sherlock, Killer!Sherlock, Cannibalism, Violence. Not for the faint of heart (or sane of mind...)!