Plot

After Panacea and her fiancé Tragicomix are kidnapped by the romans and forced to enlist in the foreign legion, Asterix and Obelix join Julius Caesar's army to rescue them.

Obelix falls for a new arrival in his home village in Gaul, but is heartbroken when her true love arrives to visit her. However, the lovers are kidnapped by Romans; Asterix and Obelix set out to rescue them on a dangerous journey that will involve gladiators, slavers and beauracracy - and a personal encounter with the Emperor himself, Julius Caesar...—Benjamin Evans <benj@whitley.unimelb.edu.au>

Julius Caesar (Serge Sauvion) is honored for successful campaigns of conquest. Gifts are brought to Rome from across the Roman Empire. Seeking to cement the celebrations, Caesar orders Caius Fatuous (Pierre Mondy), head of a prominent gladiator school, to provide him with a grand show. Meanwhile in Gaul, Asterix (Roger Carel) notices that his friend Obelix (Pierre Tornade) has begun acting strangely. Getafix (Henri Labussiere) soon reveals that he is in love with Panacea (Severine Morisot), Chief Vitalstatistix's (Jean-Pierre Darras) niece, who had recently returned. Attempting to win her affections (he gifts her flowers), Obelix becomes distraught when she is reunited with Tragicomix (Thierry Ragueneau), a much younger and handsome man who intends to marry her. Seeking to spend time together, the two lovers venture out into nearby woods, only to be ambushed by a group of Romans, led by a fresh recruit hoping to make a good impression.

When Asterix and Obelix discover what happened, they inform the village, who proceed to attack the garrison. In the aftermath, the camp's Centurion (Henri Poirier) is questioned by the Gauls as to the location of Panacea and Tragicomix. He reveals that he angrily ordered the recruit to take the prisoners away, knowing of the consequences that the recruit's actions would bring. Asterix and Obelix, joined by Dogmatix, proceed to the nearest Legion HQ for information on where the recruit went. Upon learning he was dispatched to a distant outpost in the Sahara Desert with his prisoners, they join the army in order to follow after them. Asterix is in a hurry and during his training he torments his drill instructors and also the chef, who is forced to serve good meat to all trainees.

Arriving at the desert frontier, the pair learn that Panacea and Tragicomix escaped from the Romans before their arrival. Panacea was being harassed by Roman officers and Tragicomix couldn't bear it. After deserting the Romans, Asterix and Obelix soon discover that a band of slave traders found them and sold them on to Rome. Caius, the trader, buys the guy as he is well built and will be a good performer in his gladiator show for Caeser and the girl was sold as an add-on.

In Rome, Caius wants Tragicomix and Panacea to be presented as gifts from Gaul to Caeser and they will bow to Caeser before the show in the Colosseum. But the pair refuses and Caeser respects their wishes. He orders them imprisoned in the Colosseum and to be fed to the Lions during the show.

Securing passage to the Roman capital, Asterix and Obelix learn that Panacea and Tragicomix were bought by Caius. The pair attempt to meet with him at a bathhouse, causing Caius to witness them beating up his bodyguards easily. Impressed, he orders his men to capture them for his show. Following a small argument between Asterix and Obelix, Obelix wants to dive in the pool and Asterix considers that a waste of time, that causes Asterix to misplace his magic potion, Asterix is kidnapped by Caius' men. When Obelix discovers he is missing, he proceeds to seek him out, rescuing him from a flooded cell. However, Dogmatix goes missing, after running off into the city's sewers to recover the magic potion. Without both, the pair continue to seek out Panacea and Tragicomix and quickly learn that, under Caesar's orders, Caius arranged for them to become the grand finale of the emperor's show at the Colosseum.

Seeking to gain entry, the pair go to Caius' school and secure places as gladiators the following day. The Gauls soon quickly make a mess of the show, winning a chariot race and easily beating down a number of gladiators. As lions are released to kill them, alongside Tragicomix and Panacea, Dogmatix arrives with the magic potion. The group defeat the lions with the potion, while Obelix, distracted by Panacea, accidentally shatters a third of the Colosseum. Impressed with the show, Caesar grants the Gauls their freedom and gets Caius fed to the lions in their place.

Returning home, the group arrive to their village's trademark victory feast being held in their honor. As the villagers celebrate, Asterix sits alone in a tree, after having somewhat fallen for Panacea on his return.