In a prison camp, Gérard Lacassagne meets Maurice Morand, a mysterious, anticlerical officer. Lacassagne, who aspires to enter religion, discovers that Morand himself was a priest. He swears to bring him back into the fold of the Church.

The struggle between a seminarian, Gérard Lacassagne, and a defrocked priest, Maurice Morand. They met in a prisoner of war camp and the attitude of the defrock confirms the vocation of Gérard who enters the seminary despite the painful opposition of his fiancee. The two men will then meet, confront each other, Maurice's pride colliding with Gérard's faith. Dramatic episodes follow one another and culminate on the day of Father Lacassagne's ordination. Maurice Morand kills him, but this murder suddenly opens for him, all big, the doors of the Church.