Although not a sequel, The Lamb includes three of the main characters in François Mauriac’s critically acclaimed novel La Pharisienne (1941; A Woman of the Pharisees, 1946) which appeared thirteen years earlier. Ten years older, the sadistic Jean de Mirbel, the domineering Brigitte Pian, and her stepdaughter Michele are reintroduced to play a crucial role in the tragic destruction of the young man Xavier, the lamb of the work’s title.

Although the narrative portion of the novel focuses on the seduction and sacrifice of Xavier, it is interspersed with sections of dialogue between Jean and Michele in which, after Xavier’s death, they discuss their responsibility for the young man and become reconciled to each other as husband and wife. In fact, these interchapters reveal the result of the sacrifice of Xavier, primarily the change of Jean from a cynic to one who understands the nature of love but does not fully understand the meaning of Xavier’s death.

The narrative begins with Xavier on his way by train from Bordeaux to Paris, where he will begin seminary training. He becomes fascinated with a couple on the train platform; later, when the departing man enters his compartment, he finds out that the man, a well-known local landowner named Jean de Mirbel, has left his wife. Perhaps because of what he believes to be his priestly calling, Xavier is compelled to reunite them. When Jean discovers that Xavier is about to enter the priesthood, he mocks the clergy and takes advantage of Xavier’s desire to help by convincing him to postpone his entrance into the seminary and to come with him back to his home.

When they arrive at Jean’s villa, they join not only his wife Michele but also her stepmother Brigitte Pian, Mme Pian’s secretary Dominique, and a young boy named Roland whom Michele has taken home from an orphanage to adopt. Xavier’s meeting with Dominique and the romantic and sexual attraction she has for Xavier makes him doubt his plans to enter the priesthood and to wonder if she is the real reason he has been brought to Jean’s house. He also is drawn to the child Roland after discovering that neither Jean nor Michele wants the boy. After several days during which Xavier and Dominique spend time together—mostly in company with Roland, who worships Dominique—the budding romantic situation is ended by an argument between Jean and Mme Pian as both of them maneuver for possession of the two young people—Mme Pian for Dominique and Jean for Xavier.

Although Xavier is distressed by Mme Pian’s storming out of the house and taking Dominique with her, the most distraught is Roland. Xavier decides to stay on at the villa to serve as Roland’s protector, knowing that Jean hates Roland and wishes to send him back to the orphanage. When Roland becomes hysterical at Dominique’s departure and Jean locks him in the library, Xavier finds a ladder and climbs into the boy’s room to watch over him.

Xavier goes to a local priest at Baluzac to make confession, but he finds that it is the priest who needs spiritual help more than Xavier himself. When Xavier talks of the love of Christ and the brotherhood of man, the priest angrily sends him away. Finally, Xavier draws up a will leaving his entire estate to the foundling Roland and makes arrangements with Dominique to have Roland taken in by another guardian. When Jean discovers Xavier’s plans, he drives to Baluzac to stop him. On the way there he runs into Xavier, who is on his way back to the villa on a bicycle, and kills him. The novel ends with Jean and Michele discussing the meaning of Xavier’s death and finally coming to the conclusion that they and all the others—the priest, Roland, Dominique, Brigitte—were partially responsible for the sacrificial death of the young lamb Xavier.