The Moomins, Snorkmaiden, and Little My set sail for the Riviera, facing a journey fraught with storms and desert island dangers. Snorkmaiden is dazzled by the attentions of a charmer, while Moomin learns that jealousy's sting is the most painful of all. When Moominpappa befriends an aristocrat and adopts the name 'de Moomin,' an exasperated Moominmamma retires to the relative calm of their trusty old boat. For the very first time, the unity of the Moomins is under threat.