Sir Oliver Tressilian is falsely accused of murdering Peter Godolphin, the brother of his fiancée Rosamund. Lionel, his jealous half-brother, is the true murderer. Too cowardly to own up to his crime, he has Sir Oliver sold into slavery on a Spanish galleon. When the corsairs from Algiers attack the Spanish galleon, Sir Oliver joins them, disgusted by the atrocities of the European powers. He becomes the feared "Sea Hawk," the leader of the Arab pirates in the Mediterranean. One day, Sir Oliver returns to the coast of Cornwall to take revenge on his brother and win back Rosamund.