1826, St. Petersburg. After the suppression of speeches on the Senate Square, the investigative commission begins searching for participants in the Decembrist uprising. Some of them are caught by the authorities because of informers. Suddenly, a series of brutal murders takes place in St. Petersburg: the victims are those who denounced the Decembrists. A piece of paper with lines from a poem by the young poet Alexander Pushkin invariably remains near the bodies of the murdered. A Moscow detective and a nobleman Alexander Boshnyak, released from arrest, are taking over the investigation of the case.