When the entire student body of St. Trinian's ends up at the High Court for burning down the school, it looks like curtains for the girls and the establishment. However, kindly Professor Canford keeps them out of jail with an offer to run the school in a new building and to treat the girls more respectfully and humanely.

Soon, the Professor puts his plan to improve the girls' cultural appreciation and understanding by taking the Sixth Form on a cruise around the islands of Greece - however, nothing is quite as it seems. The Professor's mysterious patron in the running of the school is none other than crook Alphonse O'Reilly, and unbeknownst to Canford, he has the boat sail to Arabia in order to sell the girls to an Emir and his 35 sons.

With Sergeant Gates once again hidden on board in order to follow the girls, and Flash Harry also accompanying the trip, various unlikely partners come together in a rescue attempt: after all, who else will protect their modesty?