Set in France during the late 1820s, when the Bourbon monarchy has been reinstated following Napoleon's defeat in a period known as the Restoration, the novel follows the rise and fall of an ambitious young man who attempts to transcend his humble origins through intelligence, willpower, and hypocrisy.
In the small provincial town of Verrières, the Mayor, M. de Rênal, is a vain man consumed by status and money. His chief rival is M. Valenod, the coarse Governor of the local poorhouse who has grown rich on public funds. Political life is shaped by the struggle between conservative royalists (called Ultras) and Liberals, with the clergy exerting considerable influence. Abbé Chélan, the town's aged
curé (parish priest), stands apart as a man of genuine integrity.
Seeking to outshine Valenod, M. de Rênal hires Julien Sorel, the 18-year-old son of a local sawmill owner, as tutor for his three sons. Julien is slim, pale, and strikingly handsome, with a fiery intellect. Despised by his father and brothers for his frailty and love of reading, he was educated by an old Surgeon-Major who taught him Latin and instilled in him an adoration of Napoleon. Recognizing that in post-Napoleonic France the Church offers a surer path to advancement than the military, Julien memorized the entire New Testament in Latin under Abbé Chélan's instruction, though his piety is strategic rather than sincere.
Madame de Rênal, the Mayor's wife, is a beautiful woman of about 30, raised in a convent with no experience of romantic love. She expects the tutor to be a rough cleric and is astonished to find instead a trembling youth whose beauty and gentleness disarm her. Julien astounds the household by reciting any page of the Latin New Testament from memory.
As weeks pass, Julien and Madame de Rênal grow closer; her marriage to the practical Mayor has left her emotionally unfulfilled. When her maid Elisa proposes marriage to Julien and he refuses, Madame de Rênal recognizes with surprise that she is developing feelings for him. One evening at the family's country house at Vergy, Julien resolves, as a matter of Napoleonic willpower rather than desire, to hold her hand. After hours of dread, he seizes it. He later announces he will come to her bedroom at two in the morning. Despite her refusal, he follows through out of rigid duty. Moved by his desperation, she yields, and their affair begins, though Julien is too preoccupied with playing a role to enjoy it. Gradually, however, he falls genuinely in love.
A royal visit to the nearby abbey of Bray-le-Haut deepens Julien's ambition: Encountering the youthful Bishop of Agde and the haughty Marquis de La Mole, he becomes convinced the Church offers the grandest prospects. When Madame de Rênal's youngest son falls gravely ill, she interprets the illness as divine punishment for her adultery and is seized by remorse. The child recovers, but the affair is exposed when the jilted Elisa reveals it to Valenod, who sends an anonymous letter to M. de Rênal. Madame de Rênal devises a plan to deflect suspicion, but Abbé Chélan, learning of the affair, orders Julien to leave for the Seminary at Besançon.
The Seminary is a grim institution. Its Director, the Abbé Pirard, is a stern Jansenist, a member of a strict Catholic faction opposed to the dominant Jesuit party, whose local leader is the Grand Vicar de Frilair, a senior diocesan official. Julien's intelligence earns him distinction but also hatred from fellow seminarians seeking comfortable church posts. Pirard becomes a reluctant protector. The Marquis de La Mole eventually offers Pirard a Parisian living and summons Julien to Paris as his secretary. Before departing, Julien secretly returns to Verrières for a final night with Madame de Rênal, narrowly escaping when a servant fires shots at him.
In Paris, Julien enters the Hôtel de La Mole, the family's grand mansion, and finds aristocratic society simultaneously magnificent and stifling. The Marquis gives Julien a blue coat for social settings, distinguishing this role from his black-coated work as secretary. A duel raises Julien's standing, and the Marquis awards him the Cross of the Legion of Honor after a diplomatic errand to London. The Marquis also involves Julien in a secret Ultra-royalist conspiracy: Julien memorizes the proceedings of a clandestine meeting and delivers them to an eminent foreign personage.
Mademoiselle Mathilde de La Mole, the Marquis's daughter, is an exceptionally intelligent, proud young woman of 19, bored by her predictable aristocratic suitors. She reveres her ancestor Boniface de La Mole, beheaded in 1574 for a political conspiracy, and wears mourning every April 30th. Mathilde notices Julien's fiery reserve and sees in him a man of extraordinary energy. She writes him a letter declaring her love and instructs him to climb a ladder to her window. Julien, suspecting a trap, arms himself but follows through. Their encounter is awkward and passionless, driven by self-image rather than genuine feeling.
The morning after, Mathilde is seized by horror at having surrendered to a social inferior. An agonizing period follows as she oscillates between contempt and attraction. On the advice of his friend Prince Korasoff, Julien courts the Maréchale de Fervaques, a pious aristocratic widow, using pre-written love letters to provoke Mathilde's jealousy. When Mathilde discovers the Maréchale's letters lying unopened in Julien's desk, she breaks down, confessing she cannot live without him. They resume their relationship.
Mathilde discovers she is pregnant and confesses everything to her father. After weeks of anguish, with Abbé Pirard as intermediary, the Marquis reluctantly provides Julien with a commission as Lieutenant of Hussars under the assumed name "Julien Sorel de La Vernaye." Julien, stationed in Strasbourg, is intoxicated with ambition.
At the height of this success, the Marquis receives a letter from Madame de Rênal, written at her confessor's dictation, describing Julien as a calculating hypocrite who uses seduction to advance himself. The Marquis withdraws his consent to the marriage. Seized by cold fury, Julien purchases pistols, enters the church in Verrières during Sunday mass, and fires twice at Madame de Rênal. The second shot strikes her in the shoulder; she is not mortally wounded. Julien is arrested.
In prison, Julien learns Madame de Rênal has survived, and relief reawakens his love, which he now recognizes as the deepest emotion of his life. Mathilde arrives and throws herself into efforts to save him, while Madame de Rênal writes to each potential juror pleading for clemency. Julien refuses to appeal, having shed his ambition entirely. He reflects that his only genuine happiness was with Madame de Rênal at Vergy.
At the trial, Julien delivers a provocative speech declaring he is being punished not for his crime but for his presumption as a peasant who dared rise above his station. The jury, led by Valenod, now a Baron, returns a unanimous verdict of guilty. In the condemned cell, Madame de Rênal visits and forgives him completely. Julien grows detached from Mathilde's efforts and prefers Madame de Rênal's company, refusing any act of hypocrisy to win clemency.
Julien faces death calmly. Mathilde retrieves his severed head and buries it in a candlelit cave on a mountaintop, reenacting the story of Marguerite de Navarre, the 16th-century queen said to have done the same for Boniface de La Mole. Madame de Rênal dies three days after the execution while embracing her children.