The aged captain Konovalov, who was forbidden by doctors for health reasons to go on fishing trips, was assigned to command the bot "Knizhnik" - a floating bench that delivers books and notebooks to fishing camps. It's a shame for the old sailor, but it's better than giving up the sea altogether. Konovalov takes several guys with him on a safe coastal voyage. On the open sea, the engine stalled, because the mechanic, Zhgutov, instead of checking and cleaning it before the voyage, drank all night with his friends. Soon a storm begins, and the boat is thrown onto the island Koldun - a bare rock in the sea. But despite all the misfortunes and hardships, the crew of the boat, except for the coward Zhgutov, did not lose courage. A minesweeper that came here took the guys and the bot crew out of this unreliable shelter.