On Christmas Eve, the submarine USS Copperfin, under the command of Captain Cassidy (Cary Grant), departs San Francisco on a secret mission. Cassidy uncovers sealed orders directing the crew to travel first to the Aleutian Islands to pick up meteorologist Raymond (John Ridgely), then on to Tokyo Bay to obtain vital weather intelligence for the upcoming Doolittle Raid. The submarine faces enemy attacks, including being targeted by two Japanese planes, resulting in tense confrontations and the loss of crewmember Mike (Tom Tully). New recruit Tommy Adams (Robert Hutton) is troubled by guilt and volunteers for a dangerous bomb-defusing assignment beneath the deck. The dynamics between the crew are explored, particularly the pain felt by Greek-American Tin Can (Dane Clark) at each Allied casualty. Raymond, who has lived in Japan, discusses the role of the Japanese military in leading the nation into war, and his hopes for a future of peace. As the Copperfin nears Tokyo Bay, the crew must navigate perilous minefields and evade detection by following a Japanese ship into the bay. A team is sent ashore for weather observations, while Tommy suffers from appendicitis and undergoes a risky improvised surgery. Raymond communicates the gathered intelligence in Japanese to avoid detection, but the bay is put on alert. The submarine manages to remain undetected, allowing the crew to witness part of the Doolittle Raid through the periscope. After rescuing Raymond and the shore team, the Copperfin slips away, later sinking an enemy aircraft carrier and surviving a damaging counterattack. Captain Cassidy successfully leads the submarine and his crew back to San Francisco. Cast: - Cary Grant as Captain Cassidy - John Garfield as Wolf - Alan Hale as Cookie Wainwright - John Ridgely as Lieut. Raymond - Dane Clark as Tin Can - Warner Anderson as Exec Officer - William Prince as Pills - Robert Hutton as Tommy Adams - Tom Tully as Mike - Faye Emerson as Mrs. Cassidy - Peter Whitney as Dakota - Eleanor Parker as Mike's wife (voice) - Warren Douglas as Diving Officer - John Forsythe as "Sparks" Reynolds - John Alvin as Sound Man - Bill Kennedy as Gunnery Officer - Ralph McColm as Ensign - William Challee as Quartermaster - Whit Bissell as Yoyo - Mark Stevens as Admiral's Aide - Jack Mower as Admiral's Aide - John Whitney as Communication Officer - George Lloyd as Chief of Boat Runtime: 135 minutes