is celebrating his victory over all of Gaul, but Lucius Detritus has kept from him that one village has managed to resist them. Detritus travels to the garrison near the village where Caius Bonus, the garrison's commanding Centurion, explains that the Gauls have a magic potion, which makes them invincible. Detritus decides to capture the potion for himself, and hearing that the clever Asterix and permanently invincible Obelix are the backbone of the Gaulish forces, attempts and fails to eliminate them. A false soothsayer arrives at the village and predicts the arrival of Romans and treasure; despite Asterix's protests, the village believe him, wherefore when a Roman tax collector arrives, they drive off his forces and take the gold. The "soothsayer" later drugs and hypnotises Asterix to create a diversion while he recaptures the tax money; but news of the theft reaches Caesar, who comes to the garrison himself, demanding the legion attack. Upon witnessing the defeat of his army, he demands Detritus subdue the village or be fed to the lions. Detritus disguises himself and some men as Druids and kidnaps Panoramix at a Druid conference. Asterix disguises Obelix as a legionary, and they enter the garrison to rescue the Druid, but are separated. Asterix joins Getafix in the dungeon, where the pair resist Detritus' demands to make the magic potion, until he tortures Idefix. Detritus uses the potion to throw Caesar into a cell, and takes command with an oblivious Obelix as his bodyguard. Obelix later helps Asterix, Getafix, Dogmatix, and Caesar escape. Caesar co-operates with the Gauls to defeat Detritus, who mounts an attack on the villagers using his own magic potion. To defeat him, Panoramix brews a special version of the potion which creates dozens of duplicates of Asterix and Obelix. Caesar is returned to power, and grants the village its freedom.
Differences from the books
It is revealed early in the film that the magic potion used by the Gauls only lasts for ten minutes. Such a short time limit is not implied in the original books, wherein the potion's effects can last for several hours, such as disguised legionary Caligula Minus holding a rock up for several hours in Asterix the Gaul or crooked adviser Codfix retaining superhuman strength until well into the daytime after drinking a ladleful of potion at night in Asterix and the Great Divide.
In the book Asterix and the Roman Agent, a character named Detritus was an agent of Caesar who was a master of manipulating people. In the movie Detritus appears to be more based on Crismus Bonus from Asterix the Gaul or Felonius Caucus from the book Asterix and the Big Fight.
The fraudulent fortune-teller Prolix is based on the character of the same name in Asterix and the Soothsayer - like in the book Asterix is the only villager who doesn't believe his false prophecies. In the film, Prolix manages to escape with stolen gold and is not seen again, whereas in the book Prolix was ultimately exposed as a phony when the Gauls managed to surprise him.
Getafix's grandfather, who appears in the movie, is not mentioned in any of the books.
In the books, Obelix's affection for Panacea was mostly comedic. In the movie, the romance is played for dramatic effect and is taken much more seriously.
The unnamed wife of village elder Geriatrix is depicted as intensely concerned about her husband getting hurt in the film - in the books Mrs Geriatrix seems to be casually dominant over her husband, who humbly does everything she tells him to.
Dogmatix appears to be Asterix's dog in the movie, not Obelix's.
