Sergey is a tutor. He rides his bike around the city all day long. He is a good teacher: he has advice and a kind word for everyone. But it is more difficult to understand your own life than even the most difficult task.

In one of the chemical laboratories in Switzerland, controlled by the CIA, work on a deadly virus — intended for military use — has been completed. Russian intelligence agencies take a special interest in the development and assign mathematician David Bronstein to obtain a sample of the potential chemical threat.