In 1930s East Africa, mining engineer John Gamble (George Brent) is falsely accused of killing his partner, Roger Smythe (Miles Mander).

Actually, the real culprit is a rival prospector, Eli Snedeker (George Tobias), a man obsessed with diamonds.

Years later, after achieving wealth, he meets and falls in love with a rich heiress, Kit Sheffield (Brenda Marshall), who turns out to be the daughter of Smythe, Gamble's dead partner.

But a fateful intervention results in a courtroom trial involving Snedeker, who has moved to London as a semi-retired diamond cutter.

Gamble/Bradley reluctantly testifies and confirms Snedeker's accusation that he is the real John Gamble, the suspected murderer of Kit's father.