Adapted from Edison Marshall's novel, an English orphan is made a servant by his uncle but escapes to a South Sea island and returns with pearls.
In the port of Bristol Arthur Blake (George Sanders) wins a boxing match and finds his orphaned nephew Benjamin Blake (Roddy McDowall), taking him from his gunsmith grandfather, Amos Kidder (Harry Davenport). Helena Blake (Kay Johnson) tells Arthur that Ben is the rightful heir; but Arthur makes Ben work in the stables, where he is beat up. Ben runs away to Amos, but rather than endanger him, he chooses to go back.
Ten years later Isabel Blake (Frances Farmer) tells Benjamin Blake (Tyrone Power) that Hobart wants to marry her, and Ben kisses her. Ben attends a masked dance, and Isabel admits she loves him. Ben says he is leaving. Arthur takes Ben to the barn and fights him, using a whip. Arthur's wife Helena tells Ben that the estate should be his and offers to help him. Ben wants to fight Arthur but, seeing his pistol, escapes. Prostitute Isabel (Elsa Lanchester) hides him and takes a message to Amos.
Ben sails on a ship that goes around South America. Caleb Green (John Carradine) uses magnets to deflect the voyage to lucrative islands, and Ben decides to join him. At night they swim ashore. Ben shows the scars on his back to gain acceptance. Ben dives for pearls and meets a beautiful woman he calls Eve (Gene Tierney), who helps. Ben kisses her, and she moves in with him. Ben teaches Eve English. He hopes for a ship but is disappointed by a derelict. Ben makes metal tools, and Eve is proud of him. A ship arrives, and Ben mediates. Caleb gives Ben his pearls and says he is staying. Ben says goodbye to Eve.
In London prominent lawyer Bartholomew Pratt (Dudley Digges) gets a pearl and sees Ben, who asks for his help to get his titles and estate and acquittal. Ben leaves him pearls and borrows a thousand pounds. Ben finds Amos in prison and gives him money. Ben goes to Arthur's house and embraces Isabel, giving her a pearl necklace. Arthur captures Ben at an inn. Amos visits Ben in jail and says that Pratt denies knowing him. In court Ben says why he defied Arthur. As Ben is about to be sentenced, Pratt comes in and proves that Ben is the lord of the estate. Arthur tells Isabel that they are ruined; but she says Ben asked to marry her. Arthur threatens to tell Ben that she betrayed him. Ben comes in and fights Arthur. Pratt reads Ben's will, and Ben sails back to the island and Eve.
This 18th-century adventure story challenges the greed
and cruelty of the unjust powerful and suggests that happiness
is found on a tropical island.