The commander of a detachment of combat swimmers, Evgeny Cherenkov, receives a new task. Disguised as a simple sailor on a passenger liner, he must arrive at a given square, jump overboard and swim to the city of Split. Our intelligence agent will be waiting for him at the pier, whom Cherenkov must deliver aboard the liner. The task is not technically difficult. But everything suddenly went wrong. Shooting began on the pier, and the intelligence agent unexpectedly ordered Cherenkov to transport a barely alive unfamiliar girl onto the liner in his place...