To save his job, David agrees to a worthless plan: picking up a mysterious package in South America. He ends up on a cruise ship with his ex Tess, his son Léo, and his colleague Stéphane, as stupid as he is clumsy, whom David uses to transport the package in his place. Everything goes wrong when Stéphane accidentally opens it: a cute baby Marsupilami appears and the trip descends into chaos! La Bande à Fifi is back, and they have a new friend…