While wandering through a mothballed Navy submarine, the U.S.S. Tiger Shark , Commander Ken White recalls the day he became the submarine's last captain: On 13 Aug 1945, in the waters of the Pacific war zone, Ken and the outgoing commander of the Tiger Shark , Josh Rice, are discussing the probable surrender of the Japanese when a downed Navy pilot is spotted. After the pilot, Lt. Commander Peter Morris, is rescued, the submarine encounters some Japanese ships and prepares to attack. Josh allows Ken, an Academy graduate with no combat experience, to issue orders, and under Ken's directions, the Tiger Shark cripples the Japanese vessels. When the submarine surfaces, however, a Japanese plane strafes the deck, and Josh is shot. The Tiger Shark then is hit by a Japanese destroyer, and to save the ship, Ken orders the submarine to crash dive, ignoring the protests of C. P. O. Boyer, who wants to rescue the stranded Josh. Soon after, Ken learns that the Japanese have surrendered and returns to pick up Josh. Josh cannot be found, however, and when the Tiger Shark later docks in California, a guilt-ridden Ken visits Josh's wife Alice and his father, Rear Admiral Joshua Rice. Although Alice and Joshua reassure Ken that he was right to put the safety of the ship first, Ken continues to be haunted by Josh's death. That night, Ken, his longtime girl friend Carol and the hard-drinking playboy Pete, whom Ken had befriended on the Tiger Shark , dine together at a nightclub. Despite his lingering depression, Ken accepts Carol's marriage proposal, and the couple announces their engagement. Years later, Ken, who has been assigned to a desk job, is asked to escort a reporter around the base's mothballed submarine fleet, and is disturbed when the visitor makes a derogatory comment about the Tiger Shark 's last captain. Ken's guilt resurfaces, especially after he learns that the submarine is being recommissioned for service in the Korean War and he is to command it. During the vessel's reconditioning, a sailor is killed in a boiler room accident, and Boyer, who also has been reassigned to the Tiger Shark , once again blames Ken. Ken grows more and more depressed until Carol finally suggests that he quit the Navy. Ken then receives a job offer from a Portland electrical company, which Carol secretly has arranged, but just as he is about to resign from the Navy, he changes his mind, declaring that he cannot run away from his problems. Carol, however, is fed up and moves out. Soon after, Ken and the Tiger Shark are sailing toward North Korea to undertake a secret mission. On the way, Ken receives a letter from Carol, who is cordial but distant. Later, when Ken meets up with Pete on an aircraft carrier, he questions him about Carol's feelings, but Pete is evasive. Ken and Pete then are briefed on their mission, which involves destroying an air radar station in Point Nokomo and a telephone center in Koyasan, so that paratroopers can land and liberate intelligence officers from a prisoner of war camp. That night, while Ken remains on board, Pete and South Korean officer Maj. Kim slip into the Point Nokomo harbor on a raft, overpower the North Korean guards and plant explosives outside the radar station. Before the bombs go off, the Tiger Shark hurries to the mine-filled port of Nokomo and releases two frogmen, who plant explosives at the telephone center. Once Ken receives signals from Pete and the frogmen, the bombs are set off, and Ken orders the submarine to surface and sends an all-clear to his superiors. The Tiger Shark is spotted and attacked by North Korean shore batteries. After the submarine suffers severe damage, Ken instructs his crew to abandon ship, and while the men are clinging to life preservers, Boyer forgives Ken. Pete then tells Ken that Carol is pregnant, and months later, a reunited Ken and Carol happily christen a new Tiger Shark , as their baby looks on.