Plot

After his home is conquered by the tyrannical emperors who now lead Rome, Lucius is forced to enter the Colosseum and must look to his past to find strength to return the glory of Rome to its people.

Rome, circa 209 A.D. Sixteen years after the demise of Emperor Marcus Aurelius and Maximus Decimus Meridius in Gladiator (2000), the Roman Empire is now ruled by the tyrannical Emperors Caracalla and Geta. As tensions mount, an enslaved Numidian leader arrives in the city as a gladiator, putting allegiances to the test. No one knows who he is, but with sinister schemes threatening the Republic, can this humble defender restore Rome to its former glory?—Nick Riganas

Sixteen years after Marcus Aurelius's death,[a] Rome is ruled by the corrupt twin emperors Geta and Caracalla. Aurelius's grandson, Lucius Verus Aurelius, lives under the alias "Hanno" with his wife Arishat in Numidia. General Acacius's Roman army invades and conquers the city, enslaving Lucius and killing Arishat. To advertise the slaves as potential gladiators, the Romans pit them against feral baboons. Lucius savagely kills a baboon, impressing the stable master Macrinus, who promises Lucius an opportunity to kill Acacius if he wins enough fights in Rome.

Acacius returns to Rome as a war hero. Geta and Caracalla arrange gladiatorial games in the Colosseum to celebrate Acacius's victory. Disillusioned with war, Acacius requests a vacation with his wife, Lucilla, but the emperors refuse and plot to conquer Persia and India. Senator Thraex throws a party for the emperors, and arranges a gladiatorial duel as entertainment. After Lucius wins, Geta asks where he is from. Lucius contemptuously recites Virgil's poetry, revealing his Roman education. Ravi, the gladiators' doctor, treats Lucius's injuries and befriends him.

In the Colosseum, Lucius emulates the late legendary gladiator Maximus to win fights. Lucilla recognizes Lucius as her son, whom she sent away from Rome as a child to protect him from assassination by rivals for the throne. During a naval battle in the Colosseum, Lucius leads his side to victory and fires a crossbow at the spectating Acacius, but fails to kill him. After the battle, Lucilla tries to reconnect with her son but Lucius angrily rebuffs her. He resents being forced to flee Rome while his mother lived in luxury, and is upset that her new lover caused his wife's death.

Lucius learns that Ravi was a former slave who won his freedom in the Colosseum. Ravi shows Lucius the gladiators' shrine to Maximus, which preserves Maximus's sword and armor. Lucilla and Acacius conspire with the senators Thraex and Gracchus to overthrow the emperors and restore the Roman Republic. Acacius also agrees to rescue Lucius from slavery. However, Thraex, who owes Macrinus money, tips off Macrinus. To gain imperial favor, Macrinus advises the emperors to arrest Lucilla and Acacius for treason.

Macrinus assigns Lucius to kill Acacius in the Colosseum. Lucius fights Acacius but declines to execute him. The Praetorian Guard execute Acacius at the emperors' command, prompting the people to riot. When Macrinus questions Lucius's refusal to kill Acacius, Lucius argues that Rome can be a better place, but Macrinus disagrees. Macrinus visits Lucilla in her cell and reveals that he was once a slave under the rule of her father, Marcus Aurelius, and will avenge himself on Rome by becoming emperor and ending the imperial dynasty.

Macrinus manipulates Caracalla into killing Geta. After Caracalla names his pet monkey as a consul, Macrinus convinces the Senate to overthrow him. He also convinces Caracalla to use Lucilla as bait in the Colosseum, with only Lucius defending her against a horde of enemies. In his plan, Lucius and Lucilla will be slaughtered, triggering another riot, which the Senate will defuse by executing Caracalla.

Lucius and Lucilla reconcile to defeat Macrinus. Lucilla informs Lucius that he is Maximus's son and gifts him her father's ring, which also belonged to Maximus and Acacius. Lucius sends Ravi with the ring to meet Acacius's legions outside Rome, requesting military aid. Lucilla is brought into the Colosseum along with the senators with whom she conspired. Armed with Maximus's sword and armor, Lucius rallies the gladiators to revolt against their enslaves and defend Lucilla from execution. Gracchus is killed in the onslaught, while Macrinus kills Caracalla before fatally shooting Lucilla. Macrinus flees the rioting city with Lucius in pursuit.

Acacius's and Macrinus's armies meet outside Rome. To avert a battle, Macrinus and Lucius duel. Although Macrinus nearly kills Lucius in a river, Lucius is inspired by his mother's voice and kills Macrinus. He reveals his true identity as the imperial heir and speaks to both armies, convincing them to build a united and progressive Rome with him. Later, Lucius mourns his parents in the Colosseum.