At the instigation of his half brother Lionel, Oliver Tressilian, a wealthy baronet, is shanghaied and blamed for the death of Peter Godolphin, brother of Oliver's fiancée, whom Lionel actually has slain. At sea Oliver is captured by Spaniards and made a galley slave, but when he escapes to the Moors he becomes Sakr-el-Bahr, the scourge of Christendom. Learning of his fiancée Rosamund Godolphin's marriage to his half brother, he kidnaps both of them, but to avoid sending her to the Basha of Algiers he surrenders to a British ship. Rosamund intercedes to save his life, and following the sacrificial death of Lionel they are married.
—AFI