The birthday celebration in a cheerful youth group ended tragically: one of the guests was stabbed to death. The suspect is Sergei Belyakov, who had quarreled with the deceased more than once. And at his birthday party he actually got into a fight with him in front of everyone... Sergei’s father hires a well-known detective in the city, Tatyana Ivanova. It is not difficult for Toi to quickly find out that his offspring is not guilty of anything. The killer, of course, is someone else. But who? Conventional investigation methods are not successful. In front of Tatyana, a man clearly involved in this case was shot dead. And then she “causes fire on herself” - literally exposing herself to the killer’s shots...