Geoffrey Thorpe (Errol Flynn) is an adventurous and dashing pirate, who feels that he should pirate the Spanish ships for the good of England. In one such battle, he overtakes a Spanish ship, and when he comes aboard, he finds Doña Maria (Brenda Marshall), a beautiful Spanish royal. He is overwhelmed by her beauty, but she will have nothing to do with him because of his pirating ways (which include taking her prized jewels). To show his noble side, he suprises her by returning the jewels, and she begins to fall for him. When the ship reaches England, Queen Elizabeth I (Dame Flora Robson) is outraged at the actions of Thorpe and demands that he quit pirating. Because he cannot do this, Thorpe is sent on a mission, and in the process, becomes a prisoner of the Spaniards. Meanwhile, Doña Maria pines for Thorpe, and when he escapes, he returns to England to uncover some deadly secrets. Exciting duels follow as Thorpe must expose the evil and win Doña Maria's heart.