In 1659, an infamous English pirate Captain Red and his cabin boy Jean-Baptiste, nicknamed "Frog", are lost on a raft in the ocean without food and supplies. They sneak aboard the passing galleon Neptune and are thrown into the brig, where they meet the ship's cook Boomako. Boomako has been imprisoned after being caught attempting to steal a golden Aztec throne that is being secretly transported in the hold. Captain Red becomes obsessed with capturing the throne for himself. Meanwhile, Frog falls in love with Maria Dolores, the niece of Maracaibo's governor, who is travelling on the Neptune as a passenger.
Captain Linares dies and the command of the ship is taken by his ruthless and ambitious first mate, lieutenant Don Alfonso de la Torre, who is also in love with Maria Dolores, although she does not reciprocate his feelings. Red and Frog, put to work along with Neptune's crew, make an attempt at instigating a mutiny. In response, Don Alfonso sentences them to death with a few other mutineers. Captain Red launches an open rebellion, which proves successful.
Putting himself in command of the Neptune, Captain Red directs the ship to a pirate cove, led by his old associate Dutch. Meeting his former crewmates, Captain Red throws a party and imprisons Don Alfonso and his officers. However, one of Dutch's hostages releases them while the pirates are partying. Don Alfonso and his men return to the Neptune and retake the ship, sailing away with the golden throne in the morning. Using the money that he has gained from Dutch, Captain Red purchases an old brig and pursues the Neptune to Maracaibo.
At night, Captain Red, Frog and Boomako sneak into the governor's residence with Maria Dolores as their hostage. Red plans to use her as a bargaining chip and force her wealthy uncle to exchange her for the golden throne. Although the governor proves to be unsympathetic for his niece's fate, he becomes more cooperative after Captain Red tortures him instead, finding out that he is suffering from gout.
As Red demands, the governor provides him with a document that entitles him to confiscate the golden throne while posing as the governor's secret messenger. However, Red and Frog fail to carry the throne out of the bay and are captured by Don Alfonso, who puts them in prison. Maria Dolores visits them in their cell. She reveals her feelings toward Jean-Baptiste as the two embrace and share a kiss. Maria Dolores returns to the Neptune, which soon sets off to Spain again, with Don Alfonso promoted to captain.
The pirates, informed by Boomako of what has happened, assault the prison the following night, releasing Red and Frog. Captain Red pursues the Neptune and launches an assault on the galleon. Red sinks his own ship, making retreat impossible, and secretly orders Boomako to prepare a boat to make off with the golden throne. In the heat of battle, Frog finds Maria Dolores and duels with Don Alfonso over her. However, in the end, he remains loyal to Captain Red, abandoning the fight with Don Alfonso to aid his leader in capturing the throne.
With the Neptune burning and beyond repair, her remaining crew and passengers flee on the boat while Red, Frog, and Boomako get away in one of their own with the golden throne in their possession. With Maria Dolores out of his reach, a furious Frog throws insults at Don Alfonso, who tries to shoot him in retaliation. However, Maria Dolores intervenes desperately, disrupting his aim, and Boomako is shot dead instead. Red and Frog leave the scene, abandoning their surviving crewmates in the water.
After a series of mutinies and shifting allegiances, Captain Red and Frog ultimately fail to secure the golden Aztec throne, with Don Alfonso regaining control of the Neptune and sailing away, while Red and Frog escape with help from their pirate allies.
The ending underscores the farcical and cyclical nature of Captain Red’s ambitions—though he schemes and mutinies his way across the seas, ultimate victory remains always out of reach. The central prize, the golden throne, slips from his grasp, and the film leaves its pirates back at sea, chasing their next improbable fortune. The finale balances comic defeat with the enduring spirit of adventure, true to the film’s satirical tone.