At the instigation of his half brother Lionel (Lloyd Hughes), Oliver Tressilian (Milton Sills), a rich baronet, is shanghaied and blamed for the death of Peter Godolphin (Wallace MacDonald), 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 Rosamund's (Enid Bennett) impending marriage to his half brother, he kidnaps both of them, but to avoid the risk of giving her to Asad-ed-Din (Frank Currier), the Basha of Algiers, he surrenders to a British ship. Rosamund intercedes to save his life, and following the death of Lionel they are married.