It is early in the fourth century AD, and Christianity has become a religion in search of a theology. Roman persecution has ended, but doctrinal debates threaten to tear the church apart as the early church fathers strive to solve a mystery inherited from their apostolic tradition: how both Father and Son might be thought of as God, and yet as distinct, without doing violence to the tenet that God is One.
Enter Arius, a Libyan priest who comes to Alexandria to preach an answer: that the Son of God is a created being of a different substance than the Father, and not fully divine. When the Archbishop condemns his teachings and banishes him from the city, Arius' local apostacy expands into a worldwide schism as bishops and clergy throughout the Mediterranean world take sides. Desperate to use the religion as a force for political unity, the Christian emperor Constantine calls a convention of bishops at Nicaea to resolve the dispute. As debate begins, a consensus answer seems out of reach--until a young Alexandrian deacon presses a solution that will forever shape orthodoxy in a different direction.