The main character of the film, Mikhail Perov, is a professional diver. In his past, he failed to become a businessman, and in the present, he has large debts because he is a gambler. One day, he receives a strange telegram asking him to come and help his old friend, Garik Sedykh. Without hesitation, Perov sets off on a journey. His younger brother, Alexander, accompanies him. Upon arriving in a small coastal town, Mikhail learns that his friend has been murdered. Before his death, Garik, who worked as a bodyguard for the thief-in-law Pereverzev, hid a case with the thief's cash in a complex underwater labyrinth. He encrypted the coordinates of the location with a code known only to Mikhail. Now, the main character must find the case and save his own life and that of his brother.