With the arrival of impulsive Lt. David Farragut (Brady), Naval Captain David Porter's (Chandler) frigate is given a new assignment. The crew and ship are to sail to the Caribbean, disguised as pirates, and stop the criminals who have been preying on America's merchant fleet. Portuguese countess Donna (Ball) comes aboard since the pirates are threatening to overthrow her government, but when she and Farragut are captured, it's the noble Porter to their rescue.