Breslau, 1919: the hideously battered, naked bodies of four sailors are discovered on an island in the River Oder. When Criminal Assistant Eberhard Mock arrives at the scene to investigate, he finds an enigmatic note addressed to him, insisting that he admit to some past mistake and become a believer. As he endeavours to piece together the elements of this brutal crime, Mock combs the brothels and drinking dens of Breslau and is drawn into an insidious game: it seems that anyone he questions during the course of the investigation is destined to become the next victim. At the same time he is haunted by appalling nightmares; only nights spent drinking and carousing can keep his phantoms at bay. Ultimately Mock uncovers a secret society which has the Criminal Assistant himself clearly in its sights.