The Duke of Diamantina is the son of Rajah Kalidasa of Krishnapoor, who was executed by the British on a false charge of supporting the rebels during the Indian Mutiny of 1857. The charge was fabricated by Sir Lumley Lawton, the British Resident at the court of Krishnapoor, who wants to seize the Rajah’s hidden treasure. Just before the execution, the Resident tells the Rajah that he will be pardoned if he reveals the location of the treasure, but the Rajah refuses. The Rajah is then tied to the muzzle of a cannon and blown to pieces. After the execution, the Resident attempts to seize the Rajah’s wife and her young son, but they are rescued by a Yankee adventurer, and taken to safety. Twenty years later, the young boy is an adult and one of the richest men in the world. The Yankee helped the Rajah’s wife to carry off the hidden treasure. He then founded a trading company for her son and expanded the wealth of the treasure tenfold by wise trading. The Duke of Diamantina (the Brazilian title assumed by the son of the dead Rajah) has but one burning ambition, and that is to hunt Sir Lumley Lawton down, destroy his reputation and kill him!