Vienna is in the grip of the worst winter for years. Amid the snow and ice, a killer embarks upon a bizarre campaign of murder. Vicious mutilation, a penchant for arcane symbols, and a seemingly random choice of victim are his most distinctive peculiarities. Detective Inspector Oskar Rheinhardt summons a young disciple of Freud - his friend Dr. Max Liebermann - to assist him with the case.

The investigation draws them into the sphere of Vienna's secret societies - a murky underworld of German literary scholars, race theorists, and scientists inspired by the new English evolutionary theories. At first, the killer's mind seems impenetrable - his behaviour and cryptic clues impervious to psychoanalytic interpretation; however, gradually, it becomes apparent that an extraordinary and shocking rationale underlies his actions ...

Against this backdrop of mystery and terror, Liebermann struggles with his own demons. The treatment of a patient suffering from paranoia erotica and his own fascination with the enigmatic Englishwoman Amelia Lydgate raise doubts concerning the propriety of his imminent marriage. To resolve the dilemma, he must entertain the unthinkable - risking disgrace and accusations of cowardice.