Captain Van Horn's (Paul Henreid) pirate ship captures a Spanish galleon with a beautiful contessa aboard. The contessa (Maureen O'Hara) is travelling from Spain to be married to the evil viceroy of Cartegena, a man she has never met. The contessa is taken to the pirate hideout as a hostage. As the captain and contessa interact they fall in love. The contessa is soon challenged by Anne Bonney (Binnie Barnes) who is the captain's former lover and also a pirate. As things progress, Anne Bonney conspires with Van Horn's pirate enemies to have the contessa returned to Cartagena to get her out of the picture and away from her lover Van Horn. As the intruige unfolds Bonney, Van Horn and his crew are betrayed by the other pirates and taken prisoner by the viceroy.
The contessa then risks her life to help the captives break out of prison. A battle ensues between the escaping pirates and the prison garrison. As Van Horn fights to protect the contessa, Anne Bonney is fatally wounded in a sword duel while protecting Van Horn's back. As she is dying, Anne Bonney gives her blessing to Van Horn and the contessa.
Van Horn, the contessa, and the pirate crew go on to win the battle, escape and sail into the sunset to resume their pirate life on the Spanish Main..