A young man from the noble Bezsonov family — Nikolai — by chance and at the behest of his heart becomes an ordinary official of the detective police. His colleagues receive him coldly, and only an experienced official, Pyotr Romanovich Shchukin, sees in the young man the future star of the investigation. Together they are trying to uncover a chain of mysterious and dangerous crimes committed either in the city slums or in the boudoir of a socialite.