At his home in Lublin, Yasha Mazur, a magician, gets out of bed and eats the breakfast that his wife, Esther, prepared. Again, he assures her that he has never been unfaithful, even on long trips such as that from which he had just returned. However, while he sits in a tavern drinking beer and discussing women, his thoughts turn to the woman with whom he is presently in love, Emilia Chrabotzky, who wants him to convert to Catholicism, marry her, and move to Italy. Yasha cannot get Emilia out of his mind, but he is reluctant to leave his childless wife, who has made Yasha the center of her life. Moreover, though, unlike his wife, he is careless in religious matters, Yasha is hesitant about rejecting his faith and his people.

Again, Yasha sets off on his travels. Near Piask, he spends the night with the unattractive Magda; her mother, Elzbieta Zbarski, who treats Yasha like a son-in-law; and Magda’s unsavory brother, Bolek, who hates Yasha. The next day, Yasha goes to Piask to visit yet another mistress, Zeftel Lekach, whose husband had disappeared after his escape from prison. Yasha spends the evening with a gang of thieves, his longtime friends, who are awed by his skills, especially his ability to pick locks, and once again urge him to join them and make a fortune.

While Yasha and Magda are on their way to Warsaw, a storm breaks, and they take refuge in a prayer house. Yasha again worries about abandoning his religion. In Warsaw, however, he has to deal with a more urgent matter: his performance schedule. As usual, he learns that he will be working for very low wages. Perhaps, he thinks, Emilia is right in thinking that he should go abroad.

When he sees the beautiful Emilia, Yasha cannot resist agreeing to her terms. He says he will become a Catholic, marry her, and take her to Italy, along with her consumptive daughter Halina and her servant, Yadwiga. Privately, however, he wonders where he will find the money. At a play with Emilia, Yasha becomes so depressed that he considers repenting, but the impulse passes. When Emilia again refuses to allow him into her bed, he becomes even more despondent.

Back at his own apartment, Yasha enjoys being coddled by Magda. Just as he sits down to dinner, however, Zeftel turns up at his door. Although Magda is furious, Yasha leaves to accompany Zeftel to the house where she is staying, fearing that the white slaver who had taken her in would take advantage of her. When he gets there, however, Yasha soon finds himself in a friendly conversation, and he spends most of the night with the white slaver and his female accomplice.

Suddenly recalling that Yadwiga had told him about a rich old man who kept his money in a safe in his apartment, Yasha steals the money he needs. However, he is unable to pick the lock and, when he jumps from the balcony of the apartment, he hurts his foot. Pursued by a watchman, he again takes refuge in a prayer house. This time, he joins in the prayers, convinced that he must return to God and Judaism.

Even though Yasha’s foot is now so bad that he fears he will not be able to perform his shows, he refuses to call a doctor. Instead, he limps off to tell Emilia that he has no money for the trip. Then, to Yasha’s horror, a police officer stops by to warn Emilia that the thief might have designs on her, since a notebook with her name in it had been left in the old man’s apartment. Certain that he will eventually be arrested, Yasha tells Emilia what he had done, but, to his amazement, she responds by rebuking him for bungling the job.

In despair, Yasha wanders into a synagogue where Lithuanian Jews are holding a service. If he were to return to Judaism, Yasha mused, he would not settle for a form so worldly. Only the strictest kind of observance could prevent him from sinning.

Back at his apartment, Yasha discovers that Magda hanged herself, but not before strangling the three animals that he used in his magic act. After Magda’s body is removed, Yasha cannot remain in his apartment, and he leaves for a hotel. However, because he did not bring his identification papers, he is turned away. Certainly, he thinks, Zeftel will help him out. At the white slaver’s house, however, Yasha receives his second shock of the night. Zeftel and the white slaver are in bed together. Yasha interprets this as a sign: God has left him nowhere to go but to God.

Three years later, Yasha the magician has become Reb Jacob the Penitent. He is back in Lublin, walled up in a tiny cell in the courtyard of his house. His foot has healed, but spiritually he is still in pain, every day remembering yet another sin for which he must be punished. Esther keeps begging him to come out, and strangers break into his meditations to ask for his prayers, to discuss theology, or just to mock him.

One day, an old friend visits with news of the world Yasha had left behind. Elzbieta is dead, Bolek is in prison, and Zeftel is married to the white slaver and running a brothel in Argentina. Irrationally, Yasha feels responsible for all of these disasters. In a long letter to him, however, Emilia says that she, not he, is to blame for their affair and assures him that she and her daughter are both well and happy. Although Emilia has remarried, she counts her days with Yasha as the happiest in her life. She insists that Yasha is basically a good, kind man and urges him not to be so hard on himself. Finally, Emilia says that she, her daughter, and even the professor think of Yasha with affection, and that, in Warsaw, he is widely admired once again.