A nobleman vows to avenge the death of his father at the hands of pirates. To this end he infiltrates the pirate band. Acting in character he is instrumental in the capture of a ship, but things are complicated when he finds that there is a young woman on board whom he wishes to protect from the threat of rape.

A Spanish vessel is captured on the high seas by pirates who bind the crew and loot and blow up the ship. The only survivors are Michel and his father: they are marooned on a desert island, and when his father dies, Michel swears to avenge his death. He joins a pirate band and proves himself by capturing a merchant ship singlehanded; thereafter, he is known as The Black Pirate. Falling in love with a girl (The Princess) on the captured ship, he saves her by keeping her hostage and holding her for ransom, but he is caught in an attempt to escape and is forced to walk the plank. Swimming ashore, he returns with a boatload of men to rescue The Princess; the crew scuttle the ship, and, swimming underwater, Michel and his men storm the pirate vessel and capture it. Michel reveals that he is a Spanish duke and offers his hand in marriage to The Princess, which she accepts.