Harvard grad Bruce McVeagh has fled San Francisco for the South Seas, where he rules as a king on a remote island. With his half-crazed first-mate 'Pearly' Gates, he keeps the natives subjugated with gin. Any who dare disobey him find brutal punishment on his dreaded torture rack. But his kingdom threatens to crash down around him when his lost love, Nancy Darrell, is shipwrecked on the island, just as the aroused natives rise up against their tormentor in an armed rebellion.

Retired gem merchant Peter J. Martin hires detective Dan McRae to guard a large diamond which he plans to present to his daughter Ruth on her twenty-first birthday. Notorious jewel thief Gentleman Joe overpowers McRae, however, and takes his place at Ruth's party.