General Hammond, head of the armed forces of a Caribbean island known as the Republic of Camagua, is about to get $5 million of syndicate money and use it to take over the government. In return, the syndicate will control all prostitution and gambling on the island. Charles Rogan is delivering a safe deposit box key to the General, so that he can access the $5 million. The IMF must recover the key so that they can stop the General's plan and get the syndicate's money.
Willy substitutes for a yacht crewman and searches the yacht while Rogan, two subordinates and Rogan's girl friend party above deck. Jim, Barney and Mimi set up at an abandoned US WWII depot, with a jail cell block and a boat. When Willy calls in to Jim to report his lack of progress, Rogan overhears on the new radio his girlfriend gave him for a present. Willy jumps overboard, is shot and disappears underwater. Meanwhile, Barney takes the boat out and pretending to be the authorities from Camagua arrests Rogan and his gang and takes them back to the jail at the depot.
Barney searches the yacht with a metal detector but finds nothing. Back at the depot, one of Rogan's gang is fake "executed," while Mimi masquerades as the General's girl, who has been arrested after the General confessed to crimes against the state. Mimi convinces Rogan and his girlfriend that Barney will help her escape and Rogan forces Barney to include him in the escape plan with a promise to share the money and a threat to expose him. The escape happens and Rogan takes Barney to the boat and shows him that the key was plastic and hidden in a flower pot. Barney knocks Rogan out and takes the key.
In the meantime, Willy washed up on Camagua shore where he was captured and arrested. The General sent out a plane which spotted the yacht. But Willy escaped, knocked out 2 guards and was able to call Jim from the communication room. He warned Jim that the General was coming and arranged a meeting place at sea.
Jim and the IMF gang get out of the depot just before the General arrives and pick up Willy, who has swum out to meet their boat.