Those Who Hunt the Night

"Those Who Hunt the Night" (also published under the title Immortal blood) is a 1988 vampire/mystery novel by Barbara Hambly. It won the Locus Award winner for Best Horror Novel in 1989.

Plot summary

The 20th century is just under way, and somebody is killing the vampires of London. Against the wishes of his fellow undead, Simon Ysidro, oldest of the London vampires, seeks the assistance of Oxford professor James Asher, former spy for the British government. Ysidro gains Asher's cooperation by threatening the life of his beautiful young wife, Lydia.

Unbeknownst to Ysidro, Asher enlists the help of Lydia, a physician with a keenly analytical mind. Asher prowls the streets and crypts of London with Ysidro, entering the dark underworld of the undead, as Lydia combs property records and medical journals for clues as to who might have the means and the motive to carry out the slaughter.

Asher's theory is that the killer must be a vampire himself, one able to remain awake and active in the daytime. Lydia develops a theory as to how such a vampire might come to be. Together Asher and Ysidro travel to Paris to seek out the mythical eldest of all vampires, who might be either the killer himself, or the key to the killer's undoing.

But what they discover shocks them all -- a horrifying threat to the living as well as the undead.