The beginning of XX century. Gentle friendship connects two classmates – Jacques Thibault and Daniel de Fontaine. Opening one of the teachers correspondence between the boys leads to a tragedy. Insulted in the best of his school mentors, who roughly mastered his treasured “gray notebook” and vilestly interpreted friendship with Daniel, Jacques and his friend decided to flee the house. In Marseilles, they vainly try to board a ship, then decide to get to Toulon on foot, but they are detained and sent home. Daniel’s departure has shaken his little sister Jenny, and she is seriously ill. Jerome de Fontanen, the father of Daniel and Jenny, left the family and appears there extremely rarely. Madame de Fontaine, a clever woman, full of nobility and dedication, is forced to lie to children all the time, explaining the absence of her father.
Otherwise, things are in the family of Thibaut. Jacques hates and fears his father – an old despot, selfish and cruel. The father treats his younger son as a criminal. The successes of the eldest son of Antoine, a medical student, flatter his ambition. He decides to send Jacques to Krui, to the correctional colony he founded for boys. Antoine is indignant at his father’s cruelty, but he can not persuade him to reverse his decision.
Several months pass. Antoine is worried about Jacques’ fate. Without his father’s knowledge, he goes to Krui and conducts an investigation in a penal colony.
Jacques settles in his older brother, who already received a doctor’s diploma, in a small apartment on the first floor of his father’s house. He renews relations with Daniel. Antoine, believing that the ban on friendship imposed by their father is unfair and absurd, he himself accompanies him to the Fontanens. Jenny Jacques does not like it – unconditionally and at first sight. She can not forgive him the evil that he caused them. Jealous of her brother, she almost rejoices that Jacques is so unattractive.
It takes a few more months. Jacques enters the Ecole Normale. Daniel is engaged in painting, editing the magazine on art and enjoying the joys of life.
Antoine is called to the bed of a girl, crushed by a van. Acting quickly and decisively, he operates it at home, at the dinner table. The merciless struggle that he waged with death for this child, is universally admired. Neighbor Rachelle, who helped him during the operation, becomes his mistress. Thanks to her, Antoine is freed from internal stiffness, becomes himself.
At the dacha, in the Maisons-Laffitte, Jenny gradually, almost against his will, changes his mind about Jacques. She sees Jacques kiss her shadow, confessing in love. Jenny is confused, she can not understand her feelings, she denies the love for Jacques.
Rachelle leaves Antoine and leaves for Africa, for his former lover Hirsch, a vicious man, dangerous, with mystical power over her.
Several years pass. Antoine is a famous successful doctor. He has a huge practice – his reception day is filled to capacity.
Antoine visits his father. Already from the very beginning of the disease, he has no doubt about her death. He is attracted to a pupil of Father Zhiz, whom he and Jacques are accustomed to consider as their sister. Antoine tries to talk to her, but she shies away from talking. Lika likes Jacques. After his disappearance, three years ago, she alone did not believe in his death. Antoine thinks a lot about his profession, about life and death, about the meaning of being. At the same time, he does not deny himself the joys and pleasures of life.
Mr. Thibaut suspects the truth, but, reassured by Antoine, is playing the scene of an edifying demise. Antoine receives a letter addressed to his younger brother. The fact that Jacques is alive does not surprise Antoine very much. He wants to find him and bring him to his dying father. Antoine reads the novel “Sister”, written by Jacques and published in a Swiss magazine, attacks the trace of a younger brother. Jacques, after three years of wandering and toiling, lives in Switzerland. He is engaged in journalism, writes stories.
Antoine finds a brother in Lausanne. Jacques vigorously revolts against the invasion of his elder brother into his new life. Nevertheless, he agrees to go with him home.
Mr. Thibaut realizes that his days are numbered. Antoine and Jacques come to Paris, but the father is already unconscious. His death shocks Antoine. Analyzing the papers of the deceased, he with melancholy understands that, despite his majestic appearance, he was an unhappy man and that although this man was his father, he did not know him at all. Life comes to Jacques, but during the conversation understands that the bonds linking them are torn forever and irrevocably. The summer of 1914 Jacques again in Switzerland. He lives surrounded by revolutionary emigration, performs a number of secret assignments of socialist organizations. The report of the terrorist act in Sarajevo causes alarm among Jacques and his associates. Arriving in Paris, Jacques discusses with Antoine current political events, trying to attract him to the struggle against the impending war. But politics is far from the interests of Antoine. He doubts the seriousness of the threat and refuses to participate in the struggle. Jerome de Fontanen, entangled in the dark machinations, tries to shoot himself in the hotel. At the bedside of the dying, Jacques meets Jenny and Daniel. Jenny tries to understand his feelings. She again has a hope for happiness with Jacques. Daniel leaves for the front. Jacques explains with Jenny, and young people indulge in their love.
The war is declared, Jacques believes that something else can be done to stop it. He writes anti-war leaflets, is going to scatter them from the plane over the front line. Jacques does not manage to fulfill his plan. At approach to positions the plane suffers an accident in the air. Heavyly wounded Jacques is mistaken for a spy, and with the retreat of French troops he is shot by a French gendarme.
1918 Antoine Thibault, poisoned at the front with mustard gas, is treated in a military hospital. After leaving there, he spends a few days in Maisons-Laffitte, where now live Jenny, Daniel, Mme de Fontanen and Liz. The war made Daniel an invalid. Jenny brings up a son, whose father was Jacques. Zhima transferred all her feelings to his child and Jenny. Antoine is thrilled to discover the features of the deceased brother in the person and character of the little Jean-Paul. He already knows that he will never recover, that he is doomed, therefore he considers the child Jacques and Jenny as the last hope for the extension of the family. Antoine keeps a diary, which daily records the clinical records of his illness, collects literature on the treatment of poisoned gases. He wants to be useful to people after death. On the threshold of death, Antoine finally understands his younger brother, soberly and without illusions assesses his life. He thinks a lot about the little son of Jacques. The last words of the diary of Antoine Thibaut: “Much easier than they think, Jean-Paul.”