The Devil’s Arithmetic opens on the first day of Passover in contemporary America—probably some time during the 1980s, as the novel was published in 1988. Twelve-year-old Hannah Stern complains to her mother about attending the Seder dinner at her grandparents’ home; Hannah finds her grandparents’ constant emphasis on remembering the past, particularly the Nazis’ treatment of the Jews during World War II, embarrassing and irritating. Hannah’s mother reminds her that both of her grandparents lost family to the Nazis, but Hannah remains reluctant.

Arriving at her grandparents’ apartment, Hannah greets her favorite aunt, Aunt Eva. Eva lives with her brother, Hannah’s grandfather, and helped raise Hannah’s father. Hannah mentions that she was named after a dead friend of Eva’s.

Later that evening, as part of the Passover ritual, Hannah is told to open the door for the prophet Elijah and welcome him in. However, when Hannah opens the apartment door, instead of finding the hall she expects, she sees a green field beneath a night sky. She turns around and finds the scene behind her has changed as well. Her family is gone, and the room has changed to an old-fashioned kitchen. A woman in old-fashioned clothes addresses Hannah as “Chaya” in a strangely accented voice. Hannah eventually realizes the woman is speaking Yiddish, but strangely, Hannah can understand her perfectly. Hannah also mentions that “Chaya” is her Hebrew name—the one she shares with her aunt Eva’s friend.

Although she is confused and frightened, Hannah concludes that this strange turn of events is either a dream or some kind of elaborate game, and she decides to play along. A man enters from outside, calling himself Hannah’s uncle Shmuel, and Hannah learns that the woman, Gitl, is his sister. She also discovers that Shmuel is planning to marry a woman from a nearby village, Fayge, the next day. The three eat dinner together; then Hannah goes to the room she apparently shares with Gitl and goes to sleep.

In the morning, Hannah wakes up and finds herself still in the house with Gitl and Shmuel. She insists that her real name is Hannah and she lives in New York, but her new companions do not take her seriously. Gitl reveals that Chaya arrived just two days earlier from Lublin, where she was ill with the same sickness that killed her parents. Gitl, Shmuel, and Hannah soon leave for Shmuel’s wedding.

When the wedding procession—including Hannah—arrives at Fayge’s village, Viosk, they see three black cars trailed by twelve army trucks in front of the synagogue. A man in a black uniform with medals steps out of one of the vehicles, prompting Hannah to ask what year it is. She learns that it is 1942—and realizes the men are Nazis. The Nazi commander explains that all Jews are being resettled for the duration of the war, and the residents of Viosk have already been taken. Chaya begins to mention concentration camps and gas chambers, but the adults dismiss her as having an overactive imagination.

The members of the wedding party, knowing their relatives have already left and accepting that they have no choice, willingly enter the army trucks. They are taken to a train station where soldiers strip them of their valuables, then herd them into two boxcars much too small to hold them all. They travel for four days and nights, during which some die from the overcrowded, suffocating conditions and lack of water.

Finally, on the fourth night, the Jews, including Hannah, are allowed to exit the train. Soldiers lead them to a line of barracks surrounded by a barbed-wire fence, and men and women are separated at the entrance. Hannah, recognizing the prison as a concentration camp, is terrified, but she resolves to be brave and stay quiet about what she knows, thus allowing the other prisoners to remain hopeful.

Along with the rest of the new prisoners, Hannah has her head shaved, and she suddenly finds that she cannot recall anything of the past, neither her own life in New York nor the World War II history she learned in school. As Hannah puts it, she is “shorn of memory” along with her hair. Next, the new prisoners all have a row of numbers tattooed on her arms. Hannah tells the man who tattoos her that she cannot remember anything; he tells her that she must try, for life cannot exist without memory.

At the concentration camp, Hannah stays close to her aunt Gitl and other members of her village. She also meets and befriends Rivka, a girl her own age who gives her advice on how to survive in the camp. Rivka tells Hannah that her own family members have all died except for her brother, whom she considers as good as dead because his job is to lead other Jews to the gas chambers. Despite her great loss—or perhaps because of it—Rivka is determined to fight; she is constantly “organizing,” as she puts it, by gathering food, clothing, and other items for the other prisoners.

As time passes, Hannah settles into a routine at the camp. Her waking hours are divided between meager meals and work—practical work to keep the camp running—as well as work sorting through possessions stolen from prisoners, dividing them into piles to send back to Germany. Inspired by Rivka, Hannah tries to help others, slipping some of her bread to the younger children. Even in the horrific environment of the camp, Hannah develops close, caring relationships with Rivka and her aunt Gitl. However, Hannah also experiences moments of almost unbearable pain, as when Reuven, a child to whom she has grown close, is sent to the gas chamber.

After a failed escape plot, several members of Hannah’s village are executed, including her uncle Shmuel. Following this latest tragedy, Hannah suddenly remembers her life in America. She tells Rivka and two other girls that although six million Jews will die in the camps, the Jewish people will live on. She tells them about Israel, with a Jewish president and a Jewish senate, and Jewish movie stars in America.

Unfortunately, while the girls are talking, they are neglecting their work. A guard notices, and he happens to need three more people to make up a full load for the gas chambers. The guard chooses to spare Hannah and take Rivka, but Hannah pushes Rivka away, tells her to run, and follows the guard instead. As Hannah walks toward the gas chamber, she tells the two girls beside her a story, a story about a girl named Hannah who lives in New Rochelle. Her last words are “Ready or not, here we come. . . .” And then the girls walk through the door to the gas chamber, into the darkness.

Suddenly Hannah finds herself looking across an apartment doorway; she turns behind her and sees her family again, still celebrating the Seder. Her grandfather asks if the prophet Elijah is coming as if no time has passed at all, and Hannah returns to the table.

As the Seder continues, Hannah recognizes the tattoo on her aunt Eva’s arm and realizes Eva is Rivka. She asks Eva about it, and Eva explains that they all changed their names when they came to America, because remembering the truth was too painful. Later that evening, Aunt Eva tells Hannah that Gitl survived the Holocaust and immigrated to Israel, where she started a rescue mission for young survivors. Gitl named the organization after her young niece, who had sacrificed herself for Rivka and died a hero in the camps—her niece named Chaya. Thus, as the story ends, Hannah finally understands the true meaning of her Hebrew name. She has now learned why remembering the Holocaust is so important for her grandparents, for Aunt Eva, and now for Hannah herself.