Honorable young Frederic, who was mistakenly apprenticed to the pirates by his partially deaf nursemaid Ruth, has decided to leave the pirate life. After letting the Pirate King -- who has a soft spot for orphans -- know that he is honor-bound to "exterminate" his former colleagues, Frederic remains on land with Ruth as the crew takes off.  Suddenly a group of young ladies appear "Climbing Over Rocky Mountain."

Frederic, who has never seen a woman besides Ruth, instantly falls in love with Mabel, one of the many daughters of "The Very Model of a Modern Major General" Stanley. Soon the other pirates return and want to marry the rest of the Major-General's daughters, but Stanley gets around the pirates by telling them he's an orphan.  Reluctantly the girls and pirates take leave.

In Act II, Major-General Stanley enlists the help of the timid police force for protection. Frederic wants to help, but the Pirate King and Ruth inform him that due to a technicality, he is still bound by duty to remain a pirate. Mabel summons the police and orders them to help her overcome the pirates, and Sergeant bemoans the fact that "A Policeman's Lot is Not a Happy One."

The pirates storm the Major-General's home in the dead of night, "With Cat-Like Tread" that sends the police into hiding.  After a very short struggle, the police give in -- but in the nick of time Ruth inform the Major-General that the pirates are all "noblemen who have gone wrong" and therefore are excellent suitors for his daughters.  Everyone pairs off happily, knowing that "Fair Days Will Shine."