Spartacus discovers the grave responsibilities and costs in his new role as a leader of freed slaves. Claudius Glaber's arrival in Capua forces Spartacus to keep his rebellious band intact.

The gladiators enter a house searching for Naevia and free the slaves. Lucretia wants to have a ritual for the gods and Doctore returns to the place he was before meeting Batiatus.

When the rebels receive news of someone they care about, Spartacus must decide whether saving one person is worth risking the lives of many.

Spartacus leads survivors through the woods, but Crixus gets separated and returns to a place of past suffering. Lucretia pries into Ilithyia's affairs, seeking influence with a powerful Roman.

Spartacus leads a bold mission to free Crixus from Roman captivity, but a storied gladiator from the House of Batiatus complicates matters. Ilithyia's scheming puts her marriage to Glaber at risk.

Spartacus urges his restless rebels to train for the defense of their new sanctuary. Lucretia and Ilithyia seek comfort from each other, while Glaber's forces swell with some deadly new recruits.

Spartacus and his rebels try to increase their numbers by freeing fighters enslaved in foreign wars. Lucretia seeks to recruit one of her husband's former gladiators to outmaneuver powerful Romans.

Spartacus gets a chance for vengeance when a prominent Roman is captured, but will he satisfy desire at the cost of the greater good? The intrigue amongst Glaber and the women surrounding him heats up.

Spartacus must convince his people to unite against a Roman assault. Lucretia struggles to be free from the commands of men who threaten her fate. Glaber's ruthlessness has consequences.

Spartacus and a few surviving people are trapped on top of the Vesuvius volcano. Glaber and Ashur guard the entrance.