In a deserted tundra on the lake, a seaplane makes an emergency landing, on board of which bank collectors carry a large amount of money. A storm begins and the plane relates to the river delta. An unknown person steals money from an airplane and kills a geologist, an accidental witness. And a few days later the ship departs from the northern port for the last navigation voyage, where a recidivist hides among the motley company of passengers, and the captain begins his own investigation...