Three skeletons were discovered during construction work in a city park. Forensic experts have established that they belong to young girls whose bodies were buried ten years ago. The case was entrusted to the operas Pafnutyev and Khudoley. Detectives find archival materials about three schoolgirls who disappeared after the prom and realize that the chances of finding the criminal are very small: too much time has passed... An incident helps move the case forward: a button with a picture of a propeller is found in the dead girl’s hand. And in the archival group photograph, only one person is shown in a uniform aviation jacket...