Olga Barkovskaya helps investigator Kartashova in the case of the kidnapping of lawyer Gennady Sinitsyn, combined with the murder of Gennady's wife Natalia. The criminal sends strange messages consisting of sequences of perfect numbers to the kidnapped man's brother, Judge Semyon Sinitsyn. Each message gives Olga a new clue and brings her closer to catching the criminal, and at the same time reveals terrible secrets from Gennady's past. Kartashova finds it suspicious that the kidnapper is helping to find himself. He is clearly playing a game with the police, the purpose of which only Olga can understand.