Gilbert and Sullivan production of soft hearted pirates who won’t plunder anyone poor or orphaned, like themselves. Set on a rocky seashore off Cornwall, Frederick has just completed his 21 year apprentice as a pirate and is receiving the congratulations of the Pirate King. Frederick reveals he was not destined to be a pirate but is one due to the error of his nursemaid Ruth, and is to leave piracy, a life he detests, to dedicate himself to the abolishment of pirates. Not knowing why their life of piracy doesn’t pay, they ask Frederick to enlighten them. He informs them that word has spread, anyone captured by the Pirates of Penzance will say they are orphans and are immediately released.
Having left the pirates and forced to take Ruth with him, Frederick stumbles across a party of ladies. On being accepted by Mabel, a daughter of Major General Stanley, he dumps Ruth. Frederick says he will change his ways if he and Mabel marry. At this, all the pirates enter accost a girl as his bride when the Major General enters. On learning they are the infamous Pirates of Penzance, he informs them that he is an orphan. The pirates release the girls.
Fighting with his conscience, the Major General confides in Frederick that he’s not an orphan, but together plan to override the pirates anyway. Frederick is visited by Ruth and the Pirate King who inform him that having been born on February 29, he has in fact only served five of his 21 years of apprenticeship. Being duty bound and at the protests of Mabel, Frederick returns to the ship to complete his apprenticeship. A pirate once more, he is obliged to tell them of the impending attack that he has planned.
With both sides aware of the other’s plans, a fight ensues in which the pirates surprisingly win. However, when the immobile Major General demands they release his men in the name of the Queen, the pirates obey and kneel in her honour. It is then revealed that the pirates are not orphans at all but ‘noble men gone wrong’. As a result, the Major General is happy to marry off his daughters to such gentlemen.