It is the mid-1930s in the English village of Vale Thorn. Sir James Ravenwood, a collector of macabre artefacts and an expert in the occult, is hosting a weekend party at his country house, Warlock's Gate, in order to celebrate the unveiling of his latest treasure-a ceremonial dagger said once to have slain a vampire. Amongst the invited guests is a rival collector, Sebastian Lynch, a man who has been receiving strange threats against his life, in the shape of wooden dolls with skulls for faces and twine nooses tied around their necks. On the night before the unveiling of the dagger, Lynch is stabbed to death in Ravenwood's private museum at Warlock's Gate, despite the fact that the doors and the windows to the museum are all locked, the only keys have been stolen, and the house itself has been secured.

It seems to be an impossible crime. One of the guests, Everett Carr, a retired judge haunted by a tragic past, has reason to suspect the truth, however, and he instigates his own investigation. When the killer strikes for a second time, Carr finds himself in a race against time to prove his theories and unmask the killer. His investigation will peel away the respectable veneer not only of the Ravenwood family but also of the houseguests, uncovering revenge, blackmail, illegitimacy, and personal tragedy, before the final secrets of Warlock's Gate are exposed.