Emperor Constantine has proclaimed Christianity the official religion of the Roman Empire, ushering in a new era for the Church. Quadratus, a young Christian soldier assigned to Constantine's bodyguard, watches as the Church is transformed from scattered groups of devoted believers to a fashionable means of political advancement. Arriving home for a visit, Quadratus finds that his younger sister, Placidia, is determined to become a nun in spite of her mother's opposition and refuses to leave her room. His older brother has left the family to become a desert hermit while his other sister lives in luxury and comfort, married to a recently-converted Christian. Meanwhile, the new freedom given to the Church is stirring up great anger among the pagan priests and the Jews. When a riot sweeps through the city, Quadratus tries valiantly to defend his home, but after it is over, he finds that Placidia has disappeared. Through the years that follow, Quadratus, Placidia and many others must struggle to remain faithful to the simple truth of the gospel in the confusing and challenging times in which they live.