In 1812, the Olive Branch , an American merchant ship owned by Captain Dorman, is returning home from an extended stay in the Far East when the crew abruptly discovers that their country is at war with England after the British brig piloted by Lieutenant Strope fires upon them. In the shelling, Dorman is killed and his daughter Corunna vows vengeance on the British. When her sweetheart, sailor Dan Marvin counsels caution instead, she contemptuously dubs him Captain Caution. Corunna and her crew are taken prisoner aboard the British ship, where they meet Lucien Argandeau, his wife Victorine and Slade, a slave trader, who are also prisoners of the British. When the British ship falls under attack, the prisoners rebel and, after overpowering their British captors, regain control of the Olive Branch . Once aboard the ship, Corunna appoints the brash Slade first mate and orders the ship to France, where she seeks papers from the American Consul that would commission the ship to fight against the British and enable her to avenge the death of her father. Upon docking in France, Slade betrays Corunna by making a deal with the British to capture the ship and turn it over to him. While Corunna meets ashore with the American Consul, the British board the ship and sail away with its crew. Afterward, the distraught Corunna meets Slade, who tells her that Marvin turned the ship over to the English and convinces her to sail away with him. Meanwhile, Marvin and the crew are held prisoner aboard a British ship, where he devises an escape plan. While Marvin distracts the soldiers by fighting a boxing match with a brute, the crew escape and commandeer a pleasure yacht. Marvin then convinces the British commander to sail the yacht after Corunna and the Olive Branch . Corunna discovers Slade's treachery when he fires upon the unarmed yacht, but Marvin remains undeterred, and in a scathing sea battle, he and his men take control of the ship. With Slade brought to justice, Corunna discovers her misjudgment of Marvin, and the lovers sail for home.