With their Magic Potion which gives them superhuman strength and is known only to their druid Getafix, they easily stand up against Rome and her laws.

He is then told by another Official about Tortuous Convolvulus, a natural troublemaker whose mere presence causes arguments, quarrels and fights.

In the Gaulish village, things are being organised for Chief Vitalstatistix's birthday, whom all enjoy except Impedimenta, who complains against the acquisition of useless presents including a mounting collection of swords, shields, stuffed fish, and menhirs.

when their presence is noted, Convolvulus has a small legionary pretend to knock out his huge comrade Magnumopus, causing the two Gauls to flee back to the village.

The real turning point in this ruse occurs when some of the deceived villagers voice their suspicions that Asterix and Getafix gave the secret of the Magic Potion to the Romans (which the latter took offensively as his ancient secrets are to be passed down only to other Druids), thus giving Asterix and Getafix an excuse to announce a self-imposed exile, with Obelix accompanying them, wherein their purpose is to expose Convolvulus and teach the other Gauls a lesson in trust.

Convolvulus sees this and informs Platypus, who calls for an immediate attack, but Getafix makes some genuine Magic Potion.

When questioned by Vitalstatistix, Asterix claims to have merely been "test[ing]" the shield intended as the chief's birthday present.