It's the middle of a hot, dusty St Petersburg summer in the late 1860s. A doctor's wife and son die suddenly and the doctor is arrested, suspected of poisoning. As investigator Porfiry Petrovich concedes, in such cases the obvious solution often turns out to be the correct solution. And in the city's stifling, stinking atmosphere, even he lacks the energy to look any deeper. But when further, apparently unconnected, murders occur, Porfiry is forced to reassess his assumptions. Delving into the hidden, squalid heart of the city, he is brought face to face with incomprehensible horror and cruelty.