The civil wars of the third century are finally ended by Emperor Diocletian, who shares rule of the empire with three co-emperors. In the eastern court and army of this powerful emperor, a young Constantine receives the training of a future leader. When Diocletian retires, Constantine returns to his father, one of the emperors in the west, who dies soon thereafter, making Constantine his successor. As emperor of Spain, Gaul, and Britain, Constantine proves his strength against his barbarian enemies. But when the other Roman emperors begin to turn on each other again, Constantine determines to put an end to such rivalries once and for all. Defeating emperor after emperor, he slowly gains control of the entire Roman Empire and establishes a new capital in the east. Along the way, he has a vision that will change the course of western civilization forever.