When a newspaper owner is murdered, his son takes over his crusade against a corrupt politician with criminal associations.

Bruce Marsden, a former millionaire fallen on bad times, marries Helen Stanhope against her mother's wishes. The ambitious Mrs. Stanhope encourages Anthony Stuart, a rich broker and rejected suitor of her daughter, to win Helen away from Marsden, and Stuart consequently hires Marsden to work in his firm. As Marsden works, Stuart lavishes his attentions on Helen, who sternly rejects all his advances. Undaunted, Stuart sends Marsden away on a business trip and invites Helen to attend an elegant reception.

In 64 A.D., Marcus Superbus is Prefect of Rome. When the Emperor Nero decides to renew persecution of the Christians, Marcus opposes him, fearing for the safety of Mercia, the Christian woman whom he loves. Through the machinations of the Empress Poppaea and other women at court, Tigellinus, Nero's agent in the war against the Christians, convinces Nero to have Mercia arrested. Marcus appeals to the emperor for mercy, but is told that she can be saved only by renouncing Christianity. Waiting to enter the arena to be killed, Mercia steadfastly refuses to reject her religion, despite Marcus' pleas. Finally, Marcus is converted by her and they enter the arena to face death together.