In a town near Moscow, right in the building of the prosecutor's office, three prosecutors were killed. The investigation was entrusted to investigator for particularly important cases Ivan Lisin. Having studied the documents that prosecutors worked with shortly before his death, Lisin comes to the conclusion: the guardians of the law were dealing with one dark story related to the murder of teacher Lydia Chekhovskaya. Moreover, the murdered prosecutors helped the criminal evade responsibility. So the triple murder is revenge? Suspicion immediately falls on the brother of the murdered teacher, but neither the investigator nor his assistants yet know that they are following the wrong path... Three alternative endings of the detective story do not allow the reader to relax for a second and force them to question literally everything...