The novel tells of a dangerous and thrilling journey of the ultra-secret submarine “Pioneer,” traveling across two oceans from Leningrad to Vladivostok. During the voyage, the crew must not only study the underwater world but also withstand the aggressive actions of the Japanese. By the will of fate, a fourteen-year-old boy, Pavel Bunyak, ends up aboard the submarine—alongside adults, he takes part in responsible operations and helps expose a saboteur who has infiltrated the vessel. With vivid and engaging strokes, the writer paints a picture of the underwater world—its inhabitants and its geography.