A band of galley slaves under leadership of Spartakis have taken over Julius Caesar's personal galley - much to its possessor's irking, for which he sends his no-good admiral Crustacius to recover the ship.
After some arguing about a safe place to disembark, the slaves decide to set sail for the only place safe from the Romans: Asterix' small Gaulish village. Crustacius, hot in pursuit and ignorant of the Gauls' reputation, prepares to attack the village. The Gauls prepare for battle, but Obelix is yet again denied a drop of Getafix's magic potion. As the Gauls return triumphant from battle, they find Obelix has drunk the remaining cauldron of magic potion - and that this overdose has turned him into stone, which was also proven that it would be dangerous to drink more magic potion.
The former galley slaves are granted refuge, and Getafix tries desperate measures to return Obelix to his normal state. He tries potions and things that stimulate his emotion (wild boar and a kiss from Panacea), and finally Obelix recovers from his stone state - but as a child! Unfortunately, Obelix also lost his super strength power, so now he can't lift anymore menhirs. He is kidnapped by Roman soldiers while trying to run away to the forest. The former slaves travel with Asterix, Wikipedia:Dogmatix Dogmatix and Getafix to rescue Obelix who is en route to Rome by galley under Crustacius' supervision. When they recover Obelix on the high seas, Getafix proposes Atlantis as their next destination in order to help Obelix recover his adult shape.
After dropping off Crustacius and his adjutant with the ever-returning pirates - who are also offered Caesar's galley to bring back to Rome for a reward, as a compensation for Asterix having (this time, accidentally) sunk their ship -, Getafix brings them to the remnants of Atlantis (the Canary Islands), where the Atlantides have found eternal youth. The Atlantides have no means to help, so the Gauls head back to the village, while the freed slaves decide to live at Atlantis as children forever, finally being free from Rome.
On their way back, the Gauls are intercepted by yet another Roman galley. Asterix is incapacitated by a catapult stone, and when the Romans want to feed him to the sharks all seems lost. Seeing his friend in danger provokes so much emotion that it triggers Obelix to transform within seconds to his former self. With all his conserved aggression from being bossed around the entire album, he first drives off the attacking Roman galley, then smashes the Roman outpost at the village before returning for the traditional village feast.
As for Crustacius, the story ends like this: When swapping Caesar's galley with the pirates for another ship, Asterix and Getafix had accidentally left the magic potion they had taken along for the trip aboard. When Crustacius gets a sip of it just before Ostia, he easily gets rid of the pirates. But when he realizes the nature of his drink, he commits the same mistake as Obelix and is turned into a statue himself. And his adjutant's dream of getting a promotion for bringing back the ship is dashed when some over-eager soldiers fire flaming Wikipedia:Ballista ballista bolts against the supposed pirate vessel.
The statue of the admiral ends up in the Circus Maximus for the lions, with Caesar expressing his hopes to a baffled Cleopatra that one day the lions may actually develop a taste for [granite]] after all...
- The character Spartakis is obviously based on actor Kirk Douglas and his role in the movie Spartacus.
- This is the only album in which two of the pirates are called by name.
- The Atlantean "palace" in the album has been modeled after the ruins of the Minoan civilization. Connections between Atlantis and Minoan Crete have also been explored in Atlantis Mystery, Indiana Jones and the Fate of Atlantis and other fiction.
- The young Obelix is shown as without his usual great strength. This means that he must be under six years old, as that was about the age he fell into the potion and presumably gained his strength (see How Obelix Fell into the Magic Potion When he was a Little Boy).
- This album has perhaps the closest thing in the Asterix series to a major character actually dying, as Admiral Crustacius is left trapped in stone form at the end of the story, without Getafix around to revert him back to normal.
- Cleopatra makes an appearance in this album alongside Julius Caesar. Her physical appearance is quite different from that seen in the album Asterix and Cleopatra. Her skin is much more of a tanned brown color, and she has a normal nose as opposed to the long and pointed one, which was the subject of a running gag in Asterix and Cleopatra.
- The young Obelix actually calls Asterix "Asterix" in this story, but in How Obelix fell in the Magic Potion When he was a Little Boy, he calls him "Athtewixth."
- This was the first volume in a very long time to break with the tradition of odd-numbered volumes being set abroad (while even-numbered volumes were set in Gaul).