A young man from the noble noble family of the Bezsonovs, Nikolai, by chance and at the behest of his heart becomes an ordinary detective police official. His colleagues receive him coldly, and only the experienced official Pyotr Romanovich Shchukin sees in the young man a future detective star. 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.