Patrick Marlowe, a British Army officer who adores his wife, kills another man when he finds her in his room; though innocent, Mary claims to be guilty to save her husband's life. Patrick takes the name of John Carew and goes to South Africa near the diamond fields; later, Mary goes with Mrs. Rivers to Africa and en route meets Anthony Walford, who falls in love with her. Patrick, who hopes to get some diamonds for Mary, is joined by Anthony on a hazardous expedition down the Munghana River; and though they find diamonds, they are attacked by natives and Anthony's leg is broken. At Anthony's request Patrick returns, but thinking Mary loves the other man, he avoids her. Following their reconciliation, an expedition finds Anthony in time to save him.