In the year 50 BC, Gaul is occupied by the Romans – nearly. But the small village of Asterix and his friends still resists the Roman legions with the aid of their druid’s magic potion, which gives superhuman strength. Learning of this potion, a Roman centurion kidnaps the druid to get the secret formula out of him.

Antoine, an accountant by trade, becomes a private detective to support his family. His wanderings lead him to transport a cargo of malachite to Le Havre, in the hope of a large bonus. With the help of his family, and despite a few mishaps, Antoine achieves his goal.