A sexual predator is at large on the streets of Imperial Vienna. The killer is no ordinary 'lust murderer' but an entirely new phenomenon, his deviance revealing the darker preoccupations of the age. Detective Inspector Oskar Rheinhardt appeals to his friend, psychoanalyst Dr. Max Liebermann, for assistance. But to understand the killer's behaviour, Liebermann must make a journey into uncharted regions of the human mind, tracking a monster whose modus operandi combines both exquisite precision and savage cruelty.