The Red and the Black is set in the fictional small town of Verrières in Franche-Comté. The town nestles in the mountains and most of its inhabitants make a living in the timber industry, from Monsieur Sorel, a local peasant who owns a sawmill to the Mayor, the esteemed and wealthy Monsieur de Rênal. M. de Rênal is a staunch Royalist, married with three children; Stendhal uses his preoccupation with wealth and status and his rivalry with Monsieur Valenod, the director of the local poorhouse to highlight the stifling nature of Restoration provincial life. In order to outdo him and educate his sons M. de Rênal announces his intention to appoint Julien Sorel, the youngest son of M. Sorel as their tutor. Julien has been taught Latin by a retired Bonapartist surgeon-major and the local Priest, M. Chélan who hopes eventually to send him to the seminary. Moreover, he is famed for his prodigious memory. M. Sorel is keen to be rid of his lazy bookworm of a son, and the two go in search of Julien, whom they discover reading the Mémorial de Sainte-Hélène (along with Rousseau's Confessions his preferred reading). The book is flung into the stream; Julien is dragged away and after haggling over the terms of Julien's employment a deal is struck. For Julien, a respectable job is the first step on a long ladder; his idolatry of Napoleon is based on his hero's meteoric rise and the extent to which he enabled those of lower birth to achieve the highest honours. In an earlier decade Julien would have emulated him and joined the army; in Restoration society a career in the Church is a swifter route to power and prestige. A sense of ambition rather than vocation constitutes Julien's 'hypocrisy'; en route for the de Rênal Chateau he visits the Church where he finds a scrap of newspaper, detailing the execution of a Louis Jenrel (an anagram of 'Julien Sorel'). This is the strongest portent of what is to come; the whole novel is however full of hints at Julien's fate, often intertwined with the blood imagery that arises from the title. Unperturbed, Julien makes his way to the Chateau.
Mme de Rênal, having expected a tyrant for a tutor is immediately struck by Julien's gentle boyish charm. Julien is equally flattered to be addressed as 'Monsieur' by a woman of such grace and standing. His new position is confirmed when M. de Rênal buys him a new suit; for Julien, a change of clothes always indicates a change of status (the 'black' of the title refers in part to his ecclesiastical habits. This change is particularly evident in the two outfits he later interchanges in the Hôtel de la Mole). Both the children and Mme. de Rênal become very taken with the new tutor, the latter in all innocence since for lack of experience and exposure to literature she has no notion of romantic love. Élisa, Mme de Rênal's chambermaid, also develops a similar affection; Mme de Rênal has the satisfaction of putting her case to Julien and seeing her rival consistently rejected. In this way she begins to sense her feelings for Julien, just as his pride and ambition urge him to embark upon a project of seduction, which he conceives in terms of 'duty'. A battle of wills, peppered with military analogies commences; Julien succeeds in holding her hand, but he suffers a set-back when he has to beg her to hide his portrait of Napoleon from her husband - she believes it is the portrait of a rival. Plagued by fears that M. Valenod can offer a higher price for Julien, M. de Rênal meanwhile raises his salary and Julien, perched on a mountain rock in a manner highly reminiscent of Romantic paintings indulges his ambitious fantasies. Mme de Rênal, now fully conscious of the implications of her feelings, including their immorality, becomes possessed by the possible existence of another lover. Julien meanwhile goes to visit his friend Fouqué, a timber merchant, who offers to go into business with him with the promise of substantial financial reward, a prospect that threatens to unsettle Julien's choice of vocation. Mme de Rênal feels his absence keenly and renews her fervent attentions on his return. Julien composes a battle-plan of seduction; during a visit to Verrières (the family are staying in their country house at Vergy) he also discovers that his mentor, the abbé Chélan has been made destitute by a Jesuit plot.
Julien finally 'triumphs' over Mme de Rênal by throwing himself tearfully at her feet, yet he is tormented by the desire to act like an accomplished seducer. All the while their love for each other becomes more firmly established and Julien's worldly knowledge is further increased by the illicit books sent him by his friend Fouqué. The narrative of their passion is interrupted by events in Verrières; a tale of petty provincial political intrigue is rapidly eclipsed by the visit of a foreign King to Verrières. Mme de Rênal contrives to arrange a place for Julien in the Guard of honour amongst Verrière's most prominent citizens, for which he dons a military uniform. The dual nature of his ambition is summed up when he attends a major religious ceremony as part of the same visit, spurs sticking out from under the folds of his cassock (if black is the colour of the church, then red represents battle). Elaborate religious ceremonies were popularised during the reign of Charles X (1824-1830) - this one may be modelled on a consecration in Rouen - and even the cynical Julien is greatly impressed, though even more so by the youth of the Bishop of Agde who presides. Above all, Julien's participation in these events reinforces the advantages of precocious social advancement, despite the ominous nature of the predominant imagery (the sacred icon appears to have its throat cut, the light seems cast in pools of blood on the floor).
Religious belief also impacts on Mme de Rênal when she believes that the illness of her youngest son, Stanislas-Xavier, is a punishment for her adultery. Their relationship undergoes further strain when Élisa, out of jealousy, confides their secret to M. Valenod. He denounces them to M. de Rênal by means of an anonymous letter and Mme de Rênal is forced to concoct an elaborate deceit, involving a forged second letter to herself, in order to pull the wool over her husband's eyes. This culminates in her requesting that Julien be sent away, adding painful separation to their difficulties. Julien profits from this time to attend a dinner at M. Valenod's, where he experiences a sense of moral and intellectual superiority for the first time; the manipulative Valenod is also heavily implicated in further Jesuit plot, under the control of the abbé de Frilair. Despite the offer of a substantial salary increase from M. Valenod, Julien, under the influence of the abbé Chélan, to whom Élisa has confessed all, resolves to settle matters in Verrières by leaving for the seminary in Besançon.
Julien's lack of worldly experience is all the more apparent in a new town; he visits a café for the first time, where he flirts with a licentious barmaid and narrowly avoids provoking a fight with another of her lovers. He meets the Director of the seminary, the worthy abbé Pirard, a Jansenist, whose favourite he rapidly becomes but soon finds himself castigated for his intelligence; a perverse legacy of the Enlightenment has been to make books the true 'enemies' of the faith. A religious ceremony brings a newly pious and remorseful Mme de Rênal to Besançon; her letters to Julien had gone unanswered (the abbé Pirard destroyed them) but a brief glimpse of her former lover is enough to make her faint. Meanwhile, the abbé Pirard's position in the seminary is becoming more and more untenable on account of his Jansenism; a powerful protector, the Marquis de la Mole offers to arrange a parish in Paris for him, which he accepts. Shortly afterwards he arranges for Julien to come and join him in the Hôtel de la Mole as the Marquis's private secretary. Julien profits from his escape to risk one last night of passion with Mme de Rênal in Verrières.