Off the coast of England, Frederic, a young man of 21, celebrates the end of his apprenticeship to a band of pirates. Their maid Ruth tells Frederic that when he was an infant, his father requested he be apprenticed to a pilot, but she misheard and brought him to the pirates.
Now that he is no longer a Pirate Apprentice, Frederic believes the Pirate way of life is wicked, and that the crew should consider a respectable lifestyle. Frederic also points out that they are terrible pirates who refuse to harm those who claim to be orphans. The Pirate King claims piracy is comparatively honest to a respectable lifestyle.
Frederic prepares to leave the pirate ship and Ruth begs him to take her with him and marry her. Though he is reluctant to marry her, he agrees and they depart. On the beach, they stumble upon a group of beautiful young women. Upon seeing them, Frederic angrily denounces Ruth for leading him to believe that she is beautiful.
Frederic asks the girls to help him reform from his pirate life.. All reject him except Mabel. She offers Frederic her pity and the two quickly fall in love.
The pirates return to storm the beach and capture the girls, intending to marry them.
Mabel’s father, the Major-General enters and objects to the girls being married against their wills. To save them he claims to be an orphan. The Pirates are sympathetic, being orphans themselves, and release the Major-General and the girls.
At the Major-General’s estate, he laments his lie, afraid that he has brought shame upon the family. The girls try to comfort him. As they do, the Police Sergeant arrives and tells them that with Frederic’s help, he is prepared to arrest the pirates.
Frederic considers this an opportunity to atone for a life of piracy. The Pirate King and Ruth enter and inform Frederic that he was to be apprenticed until his 21st birthday and, as he was born in a leap year on February 29th, he is actually only 5 years old. The Pirate King insists that Frederic honor his sense of duty and return to the pirates. Upon realizing this, Frederic tells the Pirate King of the impending attack.
Before leaving Frederic meets with Mabel to tell her he is actually only 5 years old. They agree to be faithful to each other until Frederic returns. Mabel tells the police that they will have to face the Pirates alone, not knowing the Pirates are planning an attack of their own.
At the Major-General’s estate, the Pirates attack the house. The police leap to defend the Major-General, but are easily subdued. The Sergeant begs them not to kill them in the name of Queen Victoria. Ruth reveals that the pirates are in fact nobility. The pirates free the Major-General out of their sense of loyalty to the Queen. The Major-General, happy to have the girls wed noblemen, offers the pirates their hands in marriage as thanks and everyone celebrates the approaching weddings.