Usurper tells the daring tale of Antonio Ferretti, a young man in 1890s Trenton who assumes the identity of a priest, becoming Father Mariano Luca in Denver, Colorado. Lacking any training but armed with raw charisma, Antonio stumbles through sermons and rituals yet wins over the skeptical townspeople and even the Bishop, rallying the Italian community to build a new church. Behind his confident facade, he hides a lonely heart, a forbidden love, and a secret child. As prosperity sweeps through town, temptation and tragedy test both Antonio and his flock. When his deception is finally exposed, it shatters the town's trust, yet his legacy endures, compelling the townspeople to honor him by naming the new church after the man who, despite his lies, became a true shepherd in their eyes.