Criminal investigation is investigating the case of robbery of the factory cashier. At the checkpoint of the factory of precision mechanics and optics, two criminals attack the cashier. Criminals manage to escape by the car, waiting for them around the corner. At the scene of the crime, criminal investigation officers arrive Major Dorokhov and Lieutenant Matushkin. They interview witnesses, but they did not remember properly any attackers or machine numbers, but noticed that one prevented the other from firing.

A Red Army officer Polevoy possesses a navy dirk with a secret message encrypted in its handle. The second part of a message belongs to a White army officer Nikitskiy. It's up to three young friends of Polevoy to uncover the mystery.

This simple and therefore especially touching story took place in one town, where four men arrived, each on his own business. They met by chance, but this did not stop them in two short days from taking part in the fate of each of them with good advice, and, more importantly, with a good deed...