When Holda Weisel's Cambridge professor sends her to Germany to investigate a recently discovered medieval diary written by a 14th century necromancer, she already suspects he knows more than he is letting on. The mysterious leather-bound volume exerts a diabolical influence on those who come into contact with it, including Rupert Keller, the attractive German archivist who now has care of it. Holda learns about a grisly murder two centuries earlier in the chapel where the manuscript had been concealed. As she begins to read the pages, she realises how closely that murder is linked to the occult contents of the book. She also learns that it is she who is now in acute danger. But does the menace come from without or within?