Frederic, the pirate apprentice, has reached his twenty-first birthday, and at midnight he will be free of his indenture. The pirate king announces that Frederic will then become a full-fledged member of the band. Frederic says that he served them only because he was a slave to duty; now he is going to leave the pirates. Astounded, the king asks for reasons. Frederic will not tell, but Ruth, the pirate maid of all work, confesses that she had been Frederic’s nurse when he was a baby. She had been told to apprentice him to a pilot, but being hard of hearing, she had thought the word was “pirate.” Afraid to reveal her mistake, she, too, had joined the pirates to look after her charge.

Frederic also announces that when he leaves the pirates he is going to do his best to exterminate the whole band. Individually, he loves them all, but as a crew of pirates they must be done away with. The pirates agree that they are such unsuccessful pirates, and that they can not blame him for leaving. Frederic tells them he knows why they are such poor pirates. When they remind him that he is still one of them until midnight, he feels that it is his duty to give them the benefit of his knowledge. The trouble is that they are too kindly. They never attack a weaker party and are always beaten by a stronger one. Then, too, if any captive says he is an orphan, he is set free; the pirates themselves had all been orphans. Word about the soft-hearted pirates spreads, and now everyone who is captured declares himself an orphan. The pirates know that Frederic is right, but they hate to be grim and merciless.

Asked what Ruth will do when he leaves their band, Frederic says he will take her with him. He wonders if she is attractive. Ruth declares that she is, but since he had had no opportunity to see another female face, Frederic cannot be sure. The king assures him that she is still a fine-appearing woman, but when Frederic tries to give her to the king, he will not have her.

Ruth has him almost convinced that she is a fair woman when Frederic sees a bevy of beautiful maidens approaching. Ruth, realizing that her cause is lost, admits that she has deceived him; she is forty-seven years of age. Frederic casts her aside.

Frederic hides as the girls approach, but he feels that he ought to reveal himself again as the women, believing themselves alone, prepare for a swim. When they hear his story, they are filled with pity for his plight and admiration for his handsome figure. From a sense of duty, one of the sisters, Mabel, accepts his affection. Her sisters—Kate, Edith, and Isabel—wonder whether her sense of duty would have been so strong had Frederic been less handsome.

Frederic warns the women about the pirates. Before they could escape, however, the band, led by their king, appears and seizes them. At the same time, their father, Major General Stanley, appears in search of his daughters. He brags of his great knowledge—he knows about everything but military skill. As soon as he learns something of military tactics, he will be the greatest general ever. When the pirates tell him they are going to marry his daughters, the general, much to their sorrow, begs them not to take his lovely daughters from him because he is an orphan. Unhappily, the pirates give up; they cannot harm an orphan.

Later, at his home, a ruin that he had purchased complete with ancestors, the general grieves because he had lied to the pirates. He knows that his falsehood about being an orphan will haunt him and his newly purchased ancestors. Frederic consoles him by telling him that the lie was justified to save his daughters from the pirates. At midnight, Frederic will lead the police to the outlaw band for capture. He must wait until then, because he is still one of them.

When the police enter, the women praise them for going so nobly to their deaths. The police, not cheered by the praise, agree that theirs will be a noble death. At midnight, Frederic prepares to lead them to the pirate hideout. At that moment, the pirate king and Ruth appear, laughing at a joke they had just discovered. Frederic had been born on February 29 in a leap year. Thus, he is not twenty-one years old, but only five years old. His apprenticeship will not be up until 1940. Frederic, thinking that he looks more than five years old, also laughs at that paradox.

Because Frederic is again one of the pirate band, he feels it his duty to tell the pirates that Major General Stanley is not an orphan, that he had lied. The pirates leave at once to capture the villain and to torture him for his falsehood. A struggle ensues between the pirates and the police. The pirates win, but when the police challenge them to surrender in the name of Queen Victoria, the pirates yield, for they love their queen. Before the police can take them away, Ruth enters and tells all assembled that the pirates are really noblemen gone wrong. Then the general forgives them their youthful fling and sends them back to their ranks, giving them his daughters for their brides.