Jud Duplenticy, a former boxer turned Catholic priest, is reassigned to a rural New York parish after assaulting a deacon. At Our Lady of Perpetual Fortitude, he serves under Monsignor Jefferson Wicks, a volatile priest shaped by a bitter family legacy involving a vanished fortune and a desecrated church crucifix. Jud clashes with Wicks over his inflammatory sermons, which have alienated nearly the entire congregation.

During a Good Friday service, Wicks is found stabbed to death with a knife made from a devil’s-head lamp ornament—an object Jud had drunkenly stolen days earlier—making Jud the prime suspect. Police chief Geraldine Scott brings in private detective Benoit Blanc, who recruits Jud as an assistant, convinced of his innocence. As they investigate, they uncover secrets involving the congregation, including claims that Wicks found his grandfather’s fortune and planned a political future with his illegitimate son, Cy Draven.

Jud later witnesses what appears to be Wicks resurrected from his tomb, only to awaken beside a murdered groundskeeper. Blanc ultimately reveals that parishioner Nat orchestrated Wicks’ murder, but mid-explanation, Blanc realizes the truth is more complex and halts the investigation, allowing the killer to confess voluntarily.

The church secretary, Martha, admits to masterminding the plot. Prentice Wicks had swallowed his fortune—a diamond—before killing himself. To stop Jefferson from desecrating the grave to retrieve it, Martha conspired to kill him and stage a false resurrection to restore faith. Nat betrayed her, but she poisoned him and herself. Jud grants her absolution as she dies.

A year later, Jud reopens the church as Our Lady of Perpetual Grace, the diamond secretly embedded in a new crucifix he crafted by hand.