The story opens in Jerusalem, a few weeks after Jesus' crucifixion. Saul of Tarsus, a young observant Pharisee and Roman citizen, makes a pact with his friend Reuben, a Sadducee priest, to save Israel from the threat posed by Jesus' followers. During a trip to Damascus to persecute the believers of that community, Saul is thrown to the ground and blinded by a divine light: it is Jesus himself who appears to him. Having recovered his sight thanks to Ananias, sent by the Lord, Saul converts, is baptized and changes his name to Paul. His conversion is regarded by Reuben as a betrayal.

After his conversion, Paul embarks on a long missionary journey to spread the Christian message among the pagans. He faces numerous difficulties, including persecution and opposition from his former friend Reuben, who now considers him an enemy. Despite adversity, Paul manages to establish several Christian communities and carry the gospel all the way to Rome, becoming a central figure in the spread of Christianity.