Robert Thicknesse outlines the plot of Gilbert and Sullivan's Victorian comedy and explains what all the 'ooing and arring' is about.
Act 1: Through a series of hilarious mix-ups, young Frederic was apprenticed until his 21st birthday to a singularly feeble bunch of pirates. Now he is 21 he decides to break out of the loathed profession, what with having principles and stuff. Going ashore, he instantly comes across the many daughters of Maj-Gen. Stanley, one of whom (Mabel, though technically any of them would do) agrees to marry him.
Coincidentally his lonely former pirate colleagues instantly pop up with plans to abduct said daughters. Gen. Stanley manages to dissuade them, and tells them far more than they require to know about his entirely non-military and largely irrelevant skills.
Act 2: Frederic plans to have the pirates arrested, though he again demonstrates poor judgment in enlisting the local police, fashionably paralysed by fears for their own health and safety. The Pirate King points out that – since Frederic was born on February 29th – his 21st birthday is technically still some way off, so Frederic returns to the pirates as per contract. Mabel says she’s good to wait the requisite 50 years for him.
The pirates pounce on Gen. Stanley and his daughters but lose heart when arrested “in Queen Victoria’s name”. Mabel explains that they are all aristocrats who have been led astray (it’s not clear where she gets this info) and therefore no harm was meant – they are basically just “Etonians being Etonians”. Gen. Stanley therefore awards the pirates his daughters.
Fancy that: The title was partly a joke about how G&S’s previous works, notably HMS Pinafore, had been pirated and had hundreds of unauthorised performances in the USA. To counter this, Pirates had its premiere in New York in 1879, thereby securing its US copyright.
G&S’s regular lead actor George Grossmith played General Stanley as a caricature of Sir Garnet Wolseley, one of the great military heroes of the Empire, wearing a big version of his moustache and imitating his mannerisms. Apparently Sir G was rather pleased, and took to performing the Major-General’s song as a party turn.