The plot of the novel is based on real events - the murder of an unknown man in August 1885 in the very center of the capital, in the Znamenskaya hotel. A crime without an obvious motive, which occurred under very mysterious circumstances, became widely known and caused considerable commotion among ordinary people. Together with the heroes of the novel - private detective Shumilov and the officials of the Detective Police - the reader will go through all the zigzags of the investigation, each step of which turned the picture of what happened upside down.