The narrator, an English teacher of languages living in Geneva, is narrating the personal record of Kyrilo Sidorovitch Razumov. Razumov is a student in the University of St. Petersburg in the early 1910s. He never knew his parents and thus has no family tradition. He is trusted by his fellow students, many of who hold revolutionary views, but he takes no clear positions in the great questions of his time because he considers all of Russia his family.
Mr. de P—, the brutal Minister of State, is assassinated by a team of two, but the bombs used claim the lives of his footman, the first assassin and a number of bystanders.
Razumov enters his rooms where he finds Victor Haldin, a fellow student. Haldin informs him that he was the one who murdered Mr. de P—, but he and his accomplice did not make a proper escape plan. He requests Razumov's help because he trusts him even though he realises that they do not quite belong in the same camp. Razumov agrees to help, if only to get Haldin out of his flat. Haldin tasks him with finding Ziemianitch, who was supposed to help Haldin escape.
Haldin’s request launches Razumov into a deep identity crisis as he feels that his life will be destroyed by the authorities simply out of association with Haldin. Consequently, he becomes intensely aware of his social isolation and lack of family ties. Harbouring no sympathy for Haldin's actions or his ideals, Razumov is brought closer to conservatism out of simple fear for survival. He seeks Ziemianitch and when he finds him drunk and incapacitated, beats him. Afterwards he makes up his mind to betray Haldin to save his own life and turns to his university sponsor, Prince K. They go to the chief of police, General T—. A trap is laid for Haldin.
Razumov returns to his apartment and attempts to explain his predicament to Haldin while concealing the fact that he has just betrayed him. Haldin leaves and, later that night, is caught. Razumov is distressed for days after Haldin's capture. Finally, he receives a summons to the police headquarters and meets Privy Councillor Mikulin. In a scene reminiscent of Crime and Punishment, Razumov is highly paranoid that Mikulin suspects him of being a revolutionary. Mikulin reveals that Haldin was interrogated, sentenced and hanged the same day without implicating Razumov. Mikulin also reveals that he supervised a search Razumov’s quarters and is interested in Razumov’s future plans.
The narrative shifts to Haldin's sister, Natalia, and their mother, Mrs Haldin, who live in Switzerland after Haldin persuaded them to sell their house in Russia and move. Having lived in Zurich for a while, they settled in Geneva, which has a vibrant Russian community. There, they wait for Haldin. Natalia has been friendly with the narrator for some time from whom she receives English lessons.
One day, the narrator chances upon the news of Haldin's arrest and execution in an English newspaper and tells Natalia and her mother. Natalia takes the news stoically but her mother is deeply distressed. Peter Ivanovitch, a leader in the revolutionary movement, having learnt of Haldin's execution meets with Natalia and attempts to recruit her, but Natalia is sceptical and noncommittal. He also tells her that Razumov is about to arrive in Geneva, which excites Natalia, as Haldin had described him in glowing terms in his letters.
Natalia is invited to the Chateau Borel, a big, neglected house that Madame de S— rents from the widow of an Italian banker, and meets Tekla, the abused companion of Madame de S— and secretary to Peter Ivanovitch. Tekla recounts her life story. Afterwards, they come upon Peter Ivanovitch and Razumov. Peter Ivanovitch leaves and Natalia introduces herself to Razumov.
The narrative shifts to a few weeks earlier and describes how Razumov arrived in Geneva, having first stayed in Zurich for three days with Sophia Antonovna, the right hand of Peter Ivanovitch. Razumov did not further seek Peter Ivanovitch after their first meeting but instead took long walks with Natalia, where she took him into her confidence and asked about her brother's last hours, to which Razumov gave no definite answer. Razumov is abrasive towards the narrator, who detects a deep distress under Razumov's exterior. He is invited to the Chateau Borel, where he is received on friendly terms, as Madame de S— and Peter Ivanovitch think that he was a collaborator of Haldin. In fact, Razumov he has gone to Geneva, working as a spy for the Russian government.
His taciturnity and reserve are interpreted by each character in their own way. The revolutionaries reveal some of their plans to Razumov and he is given his first assignment: to bring Natalia to Peter Ivanovitch so he can convert her, as Peter Ivanovitch cherishes female followers above everything else.
Razumov then meets Sophia Antonovna and comes to realise her as his most dangerous adversary because of her single-mindedness and perception. Suppressing his distress, he manages to deceive her. Sophia Antonovna reveals that Ziemianitch hanged himself soon after Haldin's execution, which makes the revolutionaries believe that he was the one who betrayed Haldin.
The narrative shifts back to Razumov's initial interview with Mikulin. Mikulin admits having read Razumov's private notes but reassures him that he is not suspicious of him. After telling Razumov that some of the best Russian minds ultimately returned to them (referring to Dostoevsky, Gogol and Aksakov), he lets him go. Razumov spends the next few weeks in an increasing state of malaise where he alienates his fellow students and professors. In the meantime, Mikulin has received a promotion and sees an opportunity to use Razumov. He summons him to further interviews where he recruits him, with the blessings of Prince K., to act as a secret agent for the Czarist authorities of the Russian Empire.
The narrative shifts to Geneva, where Razumov is writing his first report to Mikulin. On his way to the post office, the narrator comes upon him, but Razumov takes no notice of him. The narrator goes to Natalia's flat, only to learn that Natalia must find Razumov urgently and bring him to her dying mother, as she needs to meet the only friend of Haldin that she knows. The professor and Natalia go to the Chateau Borel to ask Peter Ivanovitch where Razumov stays. There, they find the revolutionaries preparing an insurgency in the Baltic provinces. They return to their quarters where Razumov unexpectedly visits them. After a long conversation with Natalia in which Razumov makes several obscure and cryptic remarks, and Natalia asks how her brother spent his last hours, he implies that he was the one who betrayed him.
Razumov retires to his quarters where he writes his record. He explains to Natalia that he fell in love with her as soon as she took him into her confidence and had never been shown any kind of love before, he felt he had betrayed himself by having betrayed her brother.
He mails the record to Natalia and goes to the house of Julius Laspara where a social gathering of revolutionaries is taking place. Razumov declares to the crowd that Ziemianitch was innocent and explains his motives only partially but confesses that he was the one who gave up Haldin. Some revolutionaries, led by Necator, attack him and smash his eardrums. A deaf Razumov is crushed by a tramcar and crippled. Tekla finds him and stays by his side at the hospital.
A few months pass, and Mrs Haldin has died. Natalia has returned to Russia to devote herself to charity work and gives Razumov's record to the narrator. Tekla has taken the invalid Razumov to the Russian countryside, where she looks after him.