 312 AD. Rhual, a young and athletic Gaul, is invited to take part in the gladiator games at the seaside villa of Senator Fabius Severus, near Rome. Secretly, Rhual is an agent of Emperor Constantine who wishes to establish Christianity in the Roman Empire, and Fabius is leading a movement for religious tolerance and the freeing of slaves. In the villa gardens Rhual meets and falls in love with a beautiful girl whom he later discovers to be Fabiola, the senator s daughter. Fabius is murdered during the night by reactionary politicians opposed to Christianity, and the Christians are blamed for the murder. Fabiola suspects Rhual to be one of the Christian assassins, but at their trial he appears in their defence. However, the Christians together with Rhual are found guilty and sentenced to death in the arena. So begin the persecutions during which many Christians are killed or imprisoned. The centurion Sebastian of the Praetorian Guard, denounced as a Christian, dies as a martyr. Fabiola obtains Rhual s freedom, but he at first rejects her. The situation is redeemed, however, when Fabiola declares herself to be on the side of the Christians and joins them in the arena, thereby indicating they were not responsible for her father s death. Rhual is forced to fight several gladiators, but does not attempt to kill them. Eventually, the gladiators follow his example and throw down their arms. Meanwhile, the advance troops of Constantine arrive at the city walls and there is a general uprising. Peace returns to Rome, and the imperial banners display the sign of Christ.