It’s Frederic’s 21st birthday, which also marks the end of his apprenticeship with a lively pirate band. During the celebration, Ruth, his loyal and longtime maid, admits that indenturing him to the pirates was a mistake.

The pirate crew complains that they aren’t making any profit. Frederic points out that they are terrible at pillaging the high seas. As orphans, the pirates refuse to hurt others in the same situation, but news of their kindness has spread. As a result, all potential victims also claim to be orphans themselves!

Frederic plans to go ashore and lead an honest life. He earnestly wishes the pirates would do the same, but the Pirate King objects — piracy is more honest than respectability, in his opinion. Ruth decides to leave the ship and accompany Frederic. She convinces him she is beautiful and suggests they marry, even though she is much older than he is. Naively, Frederic agrees; he hasn’t seen any other women since he was a small boy.

Frederic and Ruth arrive on the shores of Cornwall, where they meet a group of beautiful young sisters. Seeing them, Frederic realizes Ruth has misled him and rejects her marriage proposal. Eager to start fresh, Frederic confesses his feelings to the young sisters and asks if any of them will marry him.

The women are unimpressed, except for the youngest, Mabel, who feels sorry for him and agrees. Frederic and Mabel exchange promises just before the pirates arrive on the beach and try to capture all the sisters for marriage.

The pirates’ plans are thwarted when Major-General Stanley, the sisters’ father, arrives to oppose the pirates’ advances. Knowing their weakness, Major-General Stanley pretends to be an orphan. The pirates welcome him as a brother-in-arms and release his daughters. The Stanley family escapes to their estate with Frederic following.

At his estate, Major-General Stanley worries that he has dishonored his ancestors by lying about being an orphan, and his daughters try to comfort him. Meanwhile, the local Police Sergeant arrives, planning to arrest the pirates if they try to storm the estate.  

When the pirates arrive at the estate’s graveyard, Ruth and the Pirate King tell Frederic that, after reviewing the fine print of his contract, he is actually not yet free from his indentures. Since Frederic was born on February 29th (Leap Day), he’s only technically five and a quarter. 

Although Frederic is shocked and dismayed by this unexpected news, his sense of duty prevails. He agrees to rejoin the pirates and reveals to his comrades that Major-General Stanley is not an orphan. Enraged by his duplicity, the Pirate King decides to take revenge on the Major-General and his family. 

Mabel warns the Police Sergeant that Frederic won’t help them arrest the pirates now that he has rejoined the crew. The Police Sergeant and his fellow officers are discouraged by this news and become increasingly nervous about the fight ahead.  

At the Stanley estate, the pirates storm the house while police officers try to fend them off. Frederic captures Major-General Stanley, and the pirates easily overpower the police. Just when it seems all is lost for the Stanleys and the police, the Police Sergeant makes one last appeal to the pirates’ patriotism by asking them to yield in Queen Victoria’s name. Stunned, the pirates immediately comply and release all their prisoners. 

When the police turn to arrest the pirates, Ruth reveals that the entire crew consists of noblemen who have lost their way. Since they have never harmed anyone and delighted by their newfound status, Major-General Stanley forgives the pirates and offers his daughters’ hands in marriage. Everyone rejoices, and Frederic and Mabel are finally reunited for their happily-ever-after.