Riveter "Chesty" O'Conner (James Cagney) and his best friend, "Droopy" (Frank McHugh), join the US Navy to annoy O'Connor's nemesis, Chief Petty Officer "Biff" Martin (Pat O'Brien). O'Conner gets himself court-martialled for being Desertion while visiting Martin's sister Dorothy (Gloria Stuart). Disgruntled at his treatment, O'Connor angrily derides the Navy and finds himself ostracized by his fellow sailors.