An American destroyer, with a journalist on board, pursues a Russian submarine during the Cold War.

U. S. Navy Capt. Eric Finlander is the tough, efficient commander of the Bedford , an ultra-modern submarine-chasing destroyer. He has the complete loyalty of his crew, who both fear and respect him. His assistant, Commodore Schrepke, a German former U-boat commander in World War II now on assignment to NATO, is the only one who dares to question Finlander's orders or intent. The Navy permits Ben Munceford, a liberal Negro journalist, to come aboard for the purpose of writing a story about Finlander and his crew. Another newcomer, ship's doctor Lieut. Comdr. Chester Potter, discovers to his amazement that the crew never report for sick call. The Bedford is on its usual patrol off the coast of Greenland when expert sonar man Merlin Queffle detects a Russian submarine. Finlander wants to force the submarine to surface but is prohibited by fleet headquarters from doing so. Finlander stalks the submarine, keeping an around-the-clock watch, waiting for it to surface for air. Despite the warnings of Schrepke and Munceford, who sense that this mock war has gotten out of hand and fear that the Russians may show force, Finlander rams the submarine, now in international waters, when the Russians refuse to identify themselves. The crew of the Bedford is exhausted and near to cracking under the strain of keeping constant vigilance at their stations; Queffle has collapsed; and young Ensign Ralston, the butt of Finlander's criticisms, is dangerously jittery. Ralston misunderstands a command and fires a nuclear missile at the submarine, which is sunk but not before launching its own torpedoes to destroy the Bedford.