1978 horror, second in Saberhagen's loose Dracula series. In 1897,
London is getting ready for Victoria's Jubilee. A man is clubbed on
the street and loses his memory, but finds himself being used as an
experimental subject. And SHerlock Holmes will encounter the Giant Rat
of Sumatra.
All right, this isn't technically fanfic, but only on the basis
that Saberhagen got paid for it. He continues his story of Dracula as
the good guy, and combines it with Sherlock Holmes: of course they
will form an alliance to prevent dastardly deeds from being done!
There's a character who seems to be going somewhere interesting, but
ends up finding sudden death instead. Oh well. But there's also a
useful consideration of the malign influence of a bad person in a
respectable position, and the evils they can do before they're
exposed.
It's never great, and some of its virtues from the 1970s have worn
away with frequent imitation, but this is a short and enjoyable book,
at least if you find the question "what if Sherlock Holmes teamed up
with Dracula" sufficiently interesting to explore.