The Ivory of Bones

In Deuxexmycroft's Red Dragon/Silence of the Lambs Crossover "Loss of Flesh and Soul," 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.

But what happened next? This is my interpretation.