When Johan Nilsen Nagel disembarks from a steamer one midsummer evening, wearing a loud yellow suit and an oversized cap and carrying only a suitcase, a violin case, and a huge fur coat, he inevitably becomes an object of curiosity in the small Norwegian coastal town to which he has come. His eccentric appearance, his unusual behavior, and his lack of any discernible purpose for being in the town make him a bizarre and mysterious stranger. The only thing that the hotelkeeper is able to learn about his guest is that he is supposedly an agronomist who just returned from abroad and plans to spend some weeks in their town.

Nagel’s first act is to befriend Johannes Grogaard, the Midget, a grotesque but likable character who survives by playing the fool for the town sadists. One night, Nagel intervenes when the Midget is being ordered by his tormentor, the deputy Reinert, to drink a glass of beer which has been used as an ashtray and to dance and grind his teeth loudly for the amusement of the hotel cafe’s patrons. Nagel beats Reinert, drives him from the hotel, and, to the astonishment of the easily astonished townspeople, invites the Midget to his room for champagne and cigars. The Midget reveals that he is from a good family (the son of a parson and a relative of one of the authors of the country’s constitution), but since an accident (a fall from the ship’s rigging while he was a sailor), he has lived with and worked for his uncle, a coal dealer. Nagel gives him money and admonishes him to remember his family name and breeding and not to accept “clown money” any longer.

Nagel uses his friendship with the Midget to extract information from him about the townspeople who interest him. He asks about Karlsen, a young divinity student who recently committed suicide, and he asks about Dagny Kielland, whom Nagel has already encountered and frightened by his aggressive behavior. He learns that Dagny is the parson’s daughter and is engaged to a naval officer currently on duty in Malta, the son of a wealthy businessman. He manipulates the Midget into confessing that he carried a letter from Karlsen to Dagny, thus giving added weight to the rumor that the unfortunate Karlsen killed himself because of his unrequited love for her. Nagel also inquires about a woman, prematurely gray, whose eyes remind him of a woman he once loved. He learns that she is Martha Gude, a respectable spinster, the daughter of a deceased sea captain, now reduced to selling eggs for her meager living.

Nagel is invited by Dr. and Mrs. Stenersen to a party at their home, where he distinguishes himself by his loquacity and his iconoclastic views. He dismisses the Christiania (Oslo) of which they are so proud as a cultural backwater; he characterizes the celebrated Grand Cafe, gathering place of great artists, as a place where nobodies are “elated because other nobodies acknowledge them.” He is arrogant and insolent but also intriguing, particularly to Dagny Kielland, whom he walks home. When Nagel totally misrepresents his quarrel with Reinert, making himself out to be in the wrong, Dagny, who has heard of Nagel’s noble defense of the Midget, cannot understand why Nagel is lying. He confesses that it is all part of a strategy: Through such false self-denigration, he hopes eventually to appear better than he is; further, he would do anything to make her pay attention to him. At the evening’s end, Dagny’s only response is that now at least she will have something interesting to write her fiance, but Nagel has fallen deeply in love with her. He begins spending evenings near her home, hoping for a glimpse of her, and nights in the woods nearby, praying for her (or perhaps to her). When at length he confesses his passion, Dagny angrily accuses him of destroying their friendship and tells him that she wishes never to see him again.

Nagel attempts to divert himself from his obsession with Dagny by inviting Dr. Stenersen, Hansen the lawyer, Holtan the schoolmaster, Oien the student, and the Midget to a stag party. As alcohol flows freely, discussion of writers, politics, and religion becomes heated. Nagel denounces Leo Tolstoy as a mediocrity and attacks Guy de Maupassant, Victor Hugo, and particularly Henrik Ibsen. The doctor, a liberal, attacks the socialist views of the lawyer. When the talk turns to suicide, Nagel shows the group a vial of prussic acid that he keeps in a vest pocket in case of need but confesses that he lacks the courage to use it. The evening ends with everyone smashing glasses—a successful party overall, but for Nagel, unsuccessful as a diversion from his self-destructive passion for Dagny. He begins to think of Martha Gude.

Despite Nagel’s diatribes against the false nobility of charity and philanthropy, much of his time is spent in being a secret benefactor to people in need. He gives money and clothes to the Midget, always swearing him to secrecy. Posing as an antique dealer, he cultivates Martha’s friendship and tries to push a large sum of money on her in payment for a worthless broken chair. He invites her to the town bazaar. He lavishes his attention on her (at the same time looking for Dagny), dazzles her with his garrulous storytelling, awes the crowd by playing a borrowed violin, escorts her home, and proposes to her. The elaborate fantasy that he sketches for her of a cottage in the woods, a simple Edenic existence, and unending happiness seems so real and so appealing that she begins to believe him and agrees to marry him. When she changes her mind the next day, Nagel realizes that Dagny turned her against him and thus ended his only hope of tolerable life.

He throws the mysterious iron ring that he wears into the sea, goes to the woods near Dagny’s house, and drinks from his vial. When at length he finds himself still alive, he realizes that the Midget has removed the poison and substituted water. For a short time, he is ecstatic at being alive, but this mood soon gives way to depression and despair. Instead of being grateful to the Midget, Nagel is enraged to find on his return to town that the Midget has reverted to his former ways, self-abasement for money. Nagel calls him a scoundrel, accuses him of secret depravity beneath his surface goodness, and vows to rip off his mask and expose the evil which is there. Nagel falls ill and suffers Dostoevskian nightmares and hallucinations. Shaking with fever, disoriented, and desperately needing (for some unknown reason) to recover the strange ring that he threw away, he rushes to the pier, throws himself into the sea, and drowns.

The following April, Dagny and Martha talk as they return from a party where the strange story of Johan Nagel was evidently a topic of discussion. Their conversation reveals that Nagel’s intuitions about the Midget’s secret sin are correct: He was guilty of some unspecified but evil behavior toward Martha. Since Martha had told no one, Dagny marvels at how Nagel could have known.