The bell rings and Ducobu is free: at last its vacation time, far from Latouche and all his diabolical dictations! Cartoons, Club Mickey Mouse, ice-creams galore... Ducobou barely has time to celebrate before his father announces a whole other scenario: they are going away with the Gratin family.
With Léonie and her mother it's more like getting up at sparrows' fart, museums and homework. And to top it all off... Ducobou comes across Latouche and Mademoiselle Rateau, who are also on vacation at the camping ground. A nightmare!
Fortunately chance leaves a mysterious map in his path. Due to his ingenuity, Ducobu decodes the riddle and sets off to look for the pirates' lost treasure.
The king of cheating becomes the king of adventure and the true vacation can finally begin!