Pontius Pilate offers to release either Jesus of Nazareth or Barabbas, in keeping with the Passover custom. The crowd gathered for the pardoning chooses Barabbas, and Jesus is condemned to crucifixion, while Barabbas is set free. Returning to his friends, Barabbas asks for his lover, Rachel. His friends inform him that Rachel has become a follower of Christ. Rachel soon returns, but she is not happy to see Barabbas, and they tussle physically.
Barabbas witnesses the crucifixion of Jesus. As Jesus dies, the sky turns black, and Barabbas is shaken. He watches Christ's body sealed in the tomb. On the third morning, Barabbas finds the tomb open. Rachel tells him that Christ has risen, but Barabbas says it is an illusion or his followers have stolen the body. He visits the apostles; they do not know where he is, but also believe he is risen.
Rachel preaches in Jerusalem about Christ Jesus himself and is stoned to death at the insistence of the priests. Barabbas, guilt-ridden, returns to his criminal ways and tries to rob a caravan transporting several of the priests. When the robbery goes bad, Barabbas does not try to flee, and he is captured by Roman soldiers. The law forbids Pilate from executing someone who has previously been pardoned, so he sentences Barabbas to lifelong slavery in the sulfur mines of Sicily.
Barabbas survives this hellish existence for the next twenty years. He is chained to Sahak, a Christian sailor who was sent to the mines for allowing slaves to escape. Sahak at first hates Barabbas for being pardoned instead of "the Master", but the two men eventually become friends. Over time, Sahak becomes too weak to work. As the guards are about to kill him, the mine is destroyed in an earthquake, with Sahak and Barabbas the only survivors. Julia, the superstitious wife of the local prefect, considers them blessed. The prefect is due to leave for Rome, having been appointed to the Senate. Julia insists that Barabbas and Sahak accompany him for good luck.
Once in Rome, the men are trained to become gladiators by Torvald, the top gladiator in Rome. After a gladiatorial event, Sahak is overheard sharing his faith with other gladiators, and is condemned to death for treason. When a squad deliberately miss throwing their spears, Torvald executes Sahak. The next day, Torvald and Barabbas battle in the arena. Barabbas wins, killing Torvald and impressing Emperor Nero, who sets him free. Barabbas takes Sahak's corpse to the catacombs, where the local Christians are worshiping. They give him a proper burial.
Barabbas becomes lost in the catacombs. When he eventually emerges, Rome is on fire. Barabbas is told that the Christians started the fire. Believing that the end of the world has come (as Rachel and Sahak had taught), Barabbas sets fire to more buildings. He is confronted by Roman soldiers and tells them that he is a follower of Christ. He is imprisoned with several other Christians, among them the apostle Peter. Peter admonishes Barabbas for committing arson, informing him that Christians would not do such a thing. Afterwards, the Christians are executed by mass crucifixion in the persecutions that follow the fire. Having finally placed his faith in Christ, Barabbas is crucified with the others, though his last words are, "Darkness... I give myself up into your keeping... It is Barabbas".