Young orphan Geoffrey Braemer Freddie Bartholomew poses as an English aristocrat for con artists Jim Hampstead George Zucco and Doris Clandon Gale Sondergaard, who assume care of him after his parents are killed in a train wreck. He fakes fainting in a jewelry store to distract the staff, a ploy that briefly works but is ultimately interrupted by an astute insurance investigator, and Geoff is sent to Russell-Cotes, a mercantile marine school, with a stern warning: misbehavior could land him in a reformatory.
At Russell-Cotes, the headmaster Captain Briggs Charles Coburn assigns Terry O'Mulvaney Mickey Rooney to guide Geoff. Yet Geoff does not want to blend in with the other boys; his true aim is to return to London to rejoin Doris Clandon Gale Sondergaard and Jim Hampstead George Zucco, even as he waits in vain for a letter from them. He antagonizes most of the other students except the bright, relentlessly cheerful Albert Baker Terry Kilburn, who tries to keep things light.
During a town banquet, Geoff escapes his confines. Terry finds him and, after a tense confrontation, brings him back to the dormitory. But the late-night incident exposes Terry to discipline, and he is stripped of his rank, jeopardizing his coveted job on the luxury liner RMS Queen Mary. Geoff, unwilling to expose his friend, refuses to reveal who helped him escape, which stirs resentment among the other boys.
The isolation weighs on Geoff, but he begins to learn life lessons under the kind, wise instructor Crusty Jelks Herbert Mundin. Geoff eventually confesses his runaway plan to Captain Briggs, knowing it could lead to the reformatory, in part to help reinstate Terry for the Queen Mary position. He pleads with Briggs to keep the information about Terry’s role between them, sparing the others from the truth.
When Doris and Jim finally manage to contact Geoff, he chooses to reject their crooked life and declares that he will sail on the Queen Mary. The stolen necklace, though, is still a problem—Jim sews it inside Geoff’s coat and books passage on the ship bound for the United States. Briggs nonetheless selects both Terry and Geoff to join the crew of the Queen Mary, but the recovered necklace forces Geoff to face conflicting loyalties. He ultimately decides to stand with what is right, even as Doris and Jim vanish for a time, complicating his path.
Geoff is soon questioned by the police, threatening his chance to embark. Fortune smiles when one of his schoolmates recognizes Doris and Jim aboard the Queen Mary; they are arrested just in time for Geoff to board and sail with Terry, completing a journey marked by danger, loyalty, and growth.
