James Cagney is Chesty O'Connor, a tough-as-nails, always-ready-for-a-fight shipyard worker, who loses out to US Navy CPO Biff Martin (Pat O'Brien) in a fight over a girl -- he not only loses the girl, but his job, and decides he wants a rematch. But to get it, he has to join the navy, which he does, along with his buddy Droopy (Frank McHugh). And he's assigned to the same ship as Martin, but he can't goad the chief petty officer into a fight and doesn't seem to understand much about navy discipline or regulations. He manages to get on the wrong side of virtually everyone on the ship, and especially Martin, because he's attracted to the latter's sister (Gloria Stuart), who would like nothing more than to make peace between the two men in her life. None of this is close to being sorted out, along with a few misunderstandings that only worsen the feelings between the two men, before O'Connor is transferred off the ship and into a naval air service unit, as part of a dirigible crew. It's there that O'Connor begins to straighten up and fly right, and during an airborne exhibition, that he starts to show what he's really made of, in a way that neither Martin nor his sister can ever forget.