While on an expedition in Antarctica, the Count of Champignac makes an extraordinary discovery: a still-viable dinosaur egg! Having brought the precious find back to his castle, he invites a few colleagues over - along with Spirou and Fantasio - and sets about hatching the egg. But working towards scientific progress isn't easy when one is somewhat absent-minded ... and saddled with a whimsical Marsupilami 'assistant'! Soon, life in the village of Champignac becomes rather complicated ...