The story is set over the years 1588–1593 and concerns a retired Cornish seafaring gentleman, Sir Oliver Tressilian, who is villainously betrayed by a jealous half-brother.

He joins the pirates, gaining the name "Sakr-el-Bahr" (the hawk of the sea), and swears vengeance against his brother.

Oliver is betrothed to Rosamund Godolphin, whose hot-headed brother, Peter, detests the Tressilians due to an old feud between their fathers.

To avoid repercussions for Peter's death, Lionel has Oliver kidnapped and sold into slavery to ensure that he never reveals the truth.

Oliver captures a Spanish vessel and discovers his one-time kidnapper, Jasper Leigh, as a slave at the oars.

With Jasper's navigational skills, Sakr-el-Bahr sets sail for England to take revenge on Lionel.