Hired by a secret group of scientists and ex-military men, retired submarine commander Adam Jones (Widmark) takes to the helm again on a mission to investigate a possible communist nuclear base on an island in the Arctic. But danger lurks in the deep for Jones' crew, and the closer they get to their destination, the deeper their predicament gets. Hostile subs and tensions on board are only the beginning as Jones discovers that this mission isn't what it seems, and the real danger of atomic war comes from closer than he ever imagined.