The thirteenth Asterix book opens with a visit to the village by Chief Whosemoralsarelastix, a known Roman collaborator. Saying that Caesar is planning to raise taxes to fund new wars, he brought his village's treasury to the sole unconquered village in Gaul in a cauldron (that had recently held onion soup, giving the coins a distinctive odor) for safekeeping. After entrusting the cauldron to Asterix, the village holds a feast for the visiting chief and sends him on his way.
The next day, Asterix finds that someone had tunneled into his home and stolen all the sestertii from the cauldron. As punishment for failing in his duties, Vitalstatistix tells him that he must go into exile until he has either reclaimed or replaced all the silver that had been stolen from him. Asterix leaves the village, with Obelix volunteering to help him in his quest.
The two first check the local Roman camp of Compendium, only to find they don't have the money (and accidentally start a mutiny when the legionaries assume they now have to pay to be in the Legion rather than being paid). They run into the pirates (who, after being run aground by the Gauls during a previous encounter, have decided to convert their ship into a restaurant), but after beating them up, they learn that they don't have the money either (and persuade them to get out of the restaurant business and go back to sea). Heading to the nearest city, Condatum (called Rennes today), they try commerce (selling wild boars), and manage to crash the market value of pork by their poor understanding of economics. They try gladiatorial combat, only to find that the magic potion makes their victories so easy that they put the arena owner out of business. They try working in the theater, only to get their entire troupe arrested when Obelix shouts "These Romans are crazy!" in the presence of a high ranking official. They try gambling, and just lose money. They even resort to robbing a bank, only to find the bank empty due to Caesar's new taxes.
Finally, Asterix admits defeat, and decides that he must return the empty cauldron to Whosemoralsarelastix and then spend the rest of his life in exile to atone for his failure. But as he (and Obelix, who refuses to let Asterix go into exile alone) head to the chief's village, they encounter a Roman tax collector. After robbing the tax collector of enough silver to refill the cauldron, they resume their journey in much higher spirits - until Asterix realizes that the sestertii he put in the cauldron smell like onions.
Reaching Whosemoralsarelastix's cliff-top village, Asterix confronts the chieftain, saying the only plausible explanation for the coins stolen from the cauldron and the coins stolen from the tax collector both smelling like onion soup is if they were the same batch of coins. Whosemoralsarelastix was the man who stole the sestertii from Asterix's home, so that he could pay his taxes and remain in favor with the Romans, knowing that Asterix's village would do everything in their power to replace the 'stolen' money to redeem their honor after losing it, effectively making Asterix's village pay Whosemoralsarelastix's taxes for him. Realizing that he's been caught out, Whosemoralsarelastix orders his men to attack. While Obelix (who didn't understand Asterix's explanation at all) fends off the other Gauls, Asterix duels the chief. Asterix (who used up the last of his magic potion while robbing the tax collector) loses the duelnote , but before the chief can kill him, the cliff face crumbles, dropping the cauldron and the silver it held into the sea (or rather, onto the head of a certain pirate captain who coincidentally was sailing past at that moment, but the Gauls don't know that).
As Whosemoralsarelastix mourns the loss of his money, Asterix and Obelix return home with their honor restored, and are welcomed home by a feast.
- All Part of the Show: The Legionaries storming Laurensolivius' play are believed to be this by the audience.
- Bank Robbery: When they start to get desperate, Asterix and Obelix decide to rob a bank. It ends in another failure since the bank is empty due to Caesar's new taxes.
- Batman Gambit: The entire theft of Whosemoralsarelastix's gold turns out to have been a scheme from Whosemoralsarelastix himself; he stole back his own money so he could use it to pay the Romans and keep good relationships with them, while knowing full well Asterix would do everything to bring his money back- effectively allowing him to have his taxes paid by Asterix.
- Broke Episode: Variant, as Asterix and Obelix try to recover coins in a Gaul broken by Caesar's military expenditures.
- Bulk Buy Only: Due to his lack of greed (and complete ignorance of economics), Asterix ends selling fourteen wild boar for five coins. And as a Brick Joke, it causes a price fall revealed by a restaurant owner.
- Chariot Race: Asterix and Obelix visit one and try to win the money they need by gambling. They lose all their money when blindly following the poor advice of a self-proclaimed 'expert' to bet on the blue team.
- Chekhov's Gun: When Whosemoralsarelastix tells the village what he would like them to do, he mentions that the cauldron he brought full of money previously contained onion soup. When Asterix and Obelix get the money from the tax collector at the end, Asterix notices that it smells like onions...
- Comically Missing the Point:
- Obelix is also unable to get his head around the idea of throwing onion soup away from a cauldron to put money instead.
- Asterix and Obelix are in a restaurant. The waiter brings them two boars, and Asterix asks him what the building over the road is. The waiter explains that it's a bank, where the Romans keep their money. After he goes:Asterix: You know what we're going to do?
Obelix: Eat our boars?
- When Obelix is casing the bank, the guard on duty accuses him of being a potential bank robber, and boasts of the bank's security while also telling him when the guard changes and where the catch for the vault is hidden. Obelix returns to the inn where he and Asterix are staying and reports... that the guard saw straight through him before he could get any information.
- Covers Always Lie: The cover for the album shows the cauldron full of money and fitted with winged wheels, with Asterix and Obelix chasing after it. No such scene exists in the book, and even though it's probably supposed to be symbolical for the quest to retrieve the money, it's not the cauldron that's missing, just the contents.
- Creator Cameo: Goscinny and Uderzo appear in the audience at the theater. Uderzo is telling the prefect he thinks the performance should be good, while Goscinny is on the right-hand side of the picture, doing what he did best in reality: making those around him laugh.
- Cutting the Knot: Asterix comes up with a long, complex plan to break into the Roman bank, but decides to just smash their way through because trying to get Obelix to understand the plan is more trouble than it's worth.
- Doing It for the Art: In-Universe example. The actors refuse the offer of a breakout because their execution gives them an opportunity to perform in the Circus Maximus.
- Funny Background Event:
- While Asterix and Obelix are planning their bank robbery, Dogmatix gets amusingly frustrated in his attempts to enjoy a juicy bone.
- Honor Before Reason: The village exiles their greatest warrior for failing at his guard duty, and bringing dishonor to them. They very much don't want to, and Obelix calls them out on it before joining Asterix in exile, but there's nothing to be done about it, even the normally rational Getafix cant bring himself to go against Gaulish honor.
- Hollywood Density: A metal cauldron filled to the brim with silver coins would be rather heavy, but Asterix can carry it without using the magic potion, and Redbeard manages to survive the cauldron falling on his head from the top of a cliff without serious injury.
- I'll Never Tell You What I'm Telling You!: A guard tries to dissuade Obelix from robbing the bank by explaining every single detail of its security. Too bad Obelix wasn't paying attention.
- Invincible Hero: In-Universe; One of Obelix' ideas to raise money is to participate in a gladiator fight. Naturally, he easily curbstomps all eight gladiators, and the audience quickly grows bored of it.
- I Take Offense to That Last One!: Laurensolivius' play is built to shock and offend. The prefect gets way too offended once a stage frightened Obelix murmurs "These Romans are crazy", and he orders an arrest of the actors. Which the audience mistakes for part of the play.
- Les Collaborateurs: Whosemoralsarelastix is rather unpopular among Gauls for being greedy and gladly making deals with Romans for the sake of profit.
- Named After Somebody Famous: The actor who eventually hires Obelix to his play, Laurensolivius (Eleonaradus in the original French).
- Noodle Incident: Nobody says exactly what happened to the one tax collector who tried collecting taxes from Asterix's village, but whatever it was they did, nobody ever tried to do that again.Vitalstatistix: What fun we had! Remember when...?Getafix (drowns out the rest with hysterical laughter)
- Not-So-Innocent Whistle: Obelix starts whistling innocently as they break into the bank... and doesn't stop until after Asterix sees the place is empty.
- Performance Anxiety: At one point, Asterix and Obelix try their luck at performing in a theater to raise money. Unfortunately, Obelix is hit by a massive case of stage fright; his face turns pale, he starts sweating, and can only stare at he audience with open mouth. When he finally does manage to say something, it's his catchphrase These Romans are crazy, angering the Roman audience.
- Random Events Plot: The opening of the story, with Whosemoralsarelastix's money going missing, Asterix being banished, and Obelix joining him, could be followed immediately by the encounter with the tax collector. In between is a series of sketches in which Asterix completely fails to refill the cauldron and which have no role in setting up the denouement.
- Shout-Out: Obelix' stances during the bank robbery are very reminiscent of those of a western outlaw, the likes of which could be seen for instance in Lucky Luke (also written by René Goscinny).
- Speech Bubbles: The tax collector speaks entirely in forms.Tax Collector: Are you:A: Ordinary passersby?B: Motivated by friendly intentions?C: Bandits?Asterix: Give us your money if you don't want to get thumped!Tax Collector: Are you:A: Ordinary passersby?B: Motivated by friendly intentions?C: (checked) Bandits?
- Strong Family Resemblance: One of the gladiators Obelix fights is the first cousin of Lookout, the black pirate. They could be twin-brothers considering how much they look alike.
- Take That!: The tax collector is a caricature of future French President Valéry Giscard d'Estaing. When the book was written in 1968, Giscard d'Estaing was between his two tenures as Minister of Finance.
- The actors' rather shambolic and confrontational experimental theatre is a Take That to the late 60s avant-garde theatre scene.
- Throw the Dog a Bone: And for once, just for once, the pirates are happy!
- True Companions: The order of banishment applied to Asterix alone. Obelix goes with him purely out of loyalty to his friend.
- Who Would Want to Watch Us?: Obelix suggests that he and Asterix raise money by telling stories about their adventures ("We could call them The Adventures of Obelix the Gaul..."). Asterix disapproves.Asterix: I'm not much of a businessman, but I can tell you that wouldn't make any money.