Based on the true story of the Kindertransport, a rescue effort that brought approximately 10,000 children out of Nazi-occupied Europe to Britain before World War II, this novel interweaves three storylines set between December 1936 and May 1940: the rescue missions of Geertruida "Truus" Wijsmuller, a childless Dutchwoman; the coming-of-age friendship between Stephan Neuman, an aspiring Jewish playwright in Vienna, and Žofie-Helene Perger, a mathematics prodigy; and the rise of Adolf Eichmann, the Nazi bureaucrat who would later help orchestrate the Holocaust.
In December 1936, Truus smuggles three Jewish siblings across the German-Dutch border by train, bribing a Nazi guard with a ruby ring. Her husband, Joop, a frugal banker, meets them in Amsterdam. Despite years of failed pregnancies, the couple channels their longing for children into Truus's dangerous work. In Vienna, 15-year-old Stephan, son of the wealthy chocolate-making Neuman family, meets Žofie-Helene at the Burgtheater barbershop run by her grandfather Otto Perger. Žofie wears a gold infinity-symbol necklace made from her late father's tie tack; her father, a journalist, died under suspicious circumstances during a Nazi political purge. The two share an immediate intellectual bond. At the barbershop, Stephan narrowly misses meeting his literary hero Stefan Zweig, who encourages the unseen boy from the hallway. In Berlin, Adolf Eichmann, a minor functionary in the Nazi intelligence service's Jewish Department, drafts a paper arguing that Jews should be stripped of their assets and forced to emigrate.
Over the following year, Stephan and Žofie's friendship deepens as he shows her Vienna's underground tunnels and she introduces him to advanced mathematics. Stephan begins writing a play called "The Liar's Paradox," inspired by Žofie. His aunt Lisl Wirth, a cultured Jewish woman married to the gentile Michael Wirth, notices his infatuation. Truus continues smuggling children, navigating Dutch bureaucracy to secure visas for 30 orphans whose orphanage was burned by the SS, the Nazi paramilitary organization. In London, Truus and Joop meet Helen and Norman Bentwich, leaders of a British refugee aid organization, hoping to place children in England.
On March 11, 1938, Nazi mobs flood Vienna's streets as Austria surrenders in what becomes the Anschluss, Hitler's annexation of the country. Žofie leads Stephan through the underground tunnels to safety. At the Neuman palais, thugs ransack the house, destroying Stephan's manuscript. Eichmann arrives in Vienna, seizes the Palais Rothschild as headquarters, and establishes the Central Bureau for Jewish Emigration, an assembly-line system for stripping Jews of assets before granting exit visas.
Persecution escalates. Michael demands a divorce from Lisl, threatening to have Stephan's father, Herman, arrested unless the family transfers their chocolate company. Herman signs. At Prater Park, storm troopers force Stephan to goose-step after his friend Dieter identifies him as Jewish; Stephan is beaten unconscious and left with a permanent scar. He refuses to see Žofie afterward, consumed by shame. Stephan's mother, Ruchele, who has bone cancer and uses a wheelchair, urges Herman to send the boys to England, but Herman refuses. Truus has a miscarriage, her last pregnancy, and baby Adele Weiss, an infant she rescued, dies of diphtheria in a Dutch quarantine barracks. The Évian Conference, at which 32 nations discuss the refugee crisis, produces no commitments to accept Jewish refugees. The Neuman family is forced into servants' quarters as Nazis seize their possessions.
On the night of November 9, 1938, during Kristallnacht, an anti-Jewish pogrom across Nazi territory, Stephan watches from the palais roof as Herman is beaten and loaded into a truck. He flees into the underground tunnels, hiding for weeks. Stephan's younger brother, Walter, is turned away from school because Jews are no longer permitted. Stephan seeks help from Žofie's mother, Käthe Perger, editor of an anti-Nazi newspaper, who discovers that Herman died in transit to Dachau, a Nazi concentration camp. Žofie searches the tunnels for Stephan, leaving bread and her copy of Zweig's
Kaleidoscope, but Stephan watches from the shadows without revealing himself.
In London, Helen Bentwich drafts a plan to bring unaccompanied children from Nazi Germany and annexed Austria to Britain, with Jewish organizations guaranteeing financial support. Parliament approves the proposal. The Bentwiches ask Truus to negotiate directly with Eichmann. Truus travels to Vienna, is arrested in the Jewish quarter, and bluffs her way through an all-night interrogation until her captors arrange a meeting with Eichmann. In his office, Eichmann forces Truus to prove she is not Jewish, then declares that 600 children may leave if they are ready by Saturday, the Sabbath, but not one fewer. Truus and Jewish community leader Desider Friedmann organize frantically. Otto Perger brings Walter to the registration line, and Truus agrees to include Žofie but cannot take Žofie's three-year-old sister, Johanna, who is too young.
On departure day at Westbahnhof station, Stephan arrives with Walter but discovers he is number 610, 10 beyond the cutoff. He gives Walter's hand to Žofie, telling his brother she "is me" until he can follow. A desperate mother places her baby in a basket at Žofie's feet as the doors seal; Žofie takes responsibility for the infant, naming her Johanna after her own sister. Truus spots Stephan and slips him a false identity card. Žofie gives Stephan her infinity necklace with a kiss on his scarred lips.
The sealed train travels through the night with Žofie caring for 60 children alone, keeping the hidden baby quiet. At the German border, an inspection nearly exposes Stephan's false identity, but Žofie deflects the guard. The train crosses into the Netherlands to the children's cheers. After a rough North Sea ferry crossing, Helen Bentwich greets the children at Harwich, and Truus registers Stephan under his real name.
In Vienna, Ruchele entrusts Otto with 40 pre-written weekly letters so her sons will believe she is alive; the final letter, in another hand, announces her death. She unwraps a hidden razor blade, choosing to end her life on her own terms. At the Dovercourt holiday camp, prospective parents visit each Sunday but pass over older boys. Stephan writes a new play; Žofie edits it to force him to see that his refusal to separate from Walter prevents both brothers from finding homes. A couple takes baby Johanna, and the foster father, a Cambridge mathematics professor, arranges for Žofie to study there. The Smythe family takes Walter. Aunt Lisl sends a valuable portrait of herself painted by Oskar Kokoschka from Shanghai, instructing Stephan to sell it for his education.
On September 1, 1939, Käthe puts the real Johanna on the last Kindertransport from Prague and telephones Žofie at Cambridge as Gestapo officers approach. Two days later, Stephan and Žofie reunite at Liverpool Street station and share their first kiss; Stephan returns the infinity necklace. As they wait for Johanna's train, Prime Minister Chamberlain announces that Britain is at war. The train never arrives, its 250 children's fate unknown. On May 14, 1940, the day the Netherlands surrenders, Truus and Joop load 74 children onto a coal ship at IJmuiden for England. Truus remains in the occupied Netherlands, continuing to smuggle Jewish children throughout the war. The epilogue notes that most rescued children never saw their parents again, that the Wagner-Rogers Bill to bring 20,000 refugee children to America was killed by President Roosevelt, that Stefan Zweig died by suicide in exile in 1942, that Eichmann was captured and executed in 1962, and that Truus became known as "Mother of 1001 children."