Reporter Ben Munceford (Sidney Poitier) is aboard a U.S. Navy ship sailing near the Arctic Circle, on assignment to write a profile of Capt. Eric Finlander (Richard Widmark), a hardened anti-communist. Despite the concerns of Munceford, medical officer Chester Potter (Martin Balsam) and others on the ship, Finlander is shadowing a Soviet submarine on patrol in the same area, hoping to make it to surface. The cat-and-mouse game, however, turns deadly serious.