Set in the final days of World War II and its aftermath, the novel follows Marta Nederman, a young Polish Jewish woman, from the brink of death in a Nazi prison through years of loss, espionage, and rediscovered love.
Marta lies near death in a prison cell at Dachau, a Nazi concentration camp near Munich. Months earlier, she shot and killed Kommandant Richwalder, a Nazi officer, on a railway bridge in Kraków to save her best friend Emma, who had been working undercover for the resistance. The Kommandant wounded Marta before he died, and the Gestapo, the Nazi secret police, arrested her. Marta urged Emma to flee into Slovakia with her husband, Jacob, another resistance fighter. Throughout months of interrogation, Marta revealed nothing. American soldiers liberate the prison. One of them, Paul, enters Marta's cell and tends to her with extraordinary gentleness. She whispers her name before losing consciousness.
She awakens more than a week later in a displaced persons camp for war refugees near Salzburg, Austria. A nurse named Dava, a Russian-born Jewish woman, explains that the war in Europe is over. A gravely ill young woman named Rose is placed beside Marta, and the two form a close bond.
When refugees arrive at the camp, Marta volunteers to help and encounters Paul again. He remembers her and chooses to stay behind rather than join his fellow soldiers in Salzburg. They spend an afternoon on a lake. Paul is from a tobacco ranch in North Carolina, attended Princeton, and his fiancée recently ended their engagement. At dawn, as Paul's convoy prepares to depart, Marta initiates a kiss on the lakeshore.
Returning to the ward, Marta learns Rose died during the night. Dava reveals Rose had a visa to live with her aunt in London and asked that it be given to Marta. Because the visa expires the next day, Marta must leave that evening. She agrees, wanting to deliver Rose's belongings and the news of her death personally. Dava arranges false papers under Rose's name and provides money and tickets.
A train detour to Paris causes Marta to miss the ferry and the visa's expiration. The next day, she spots Paul at a café and they reunite. Using a military connection, Paul persuades the British embassy to extend the visa. That evening, they learn Japan has surrendered. When Marta tries to leave in a taxi, Paul leaps onto the moving cab and proposes. She accepts. They spend the night together, agreeing to raise any children as Jewish. Paul gives her his dog tags as a placeholder for a ring, and they plan to meet at Kings Cross Station in London on August 30.
On the ferry to England, Marta meets Simon Gold, a British diplomat working on Eastern European affairs for the Foreign Office. In London, she delivers the news of Rose's death to Rose's aunt, Delia LeMay, who insists Marta stay until Paul arrives.
On August 30, Paul does not come. The next morning, a newspaper announces that an American military plane has crashed in the English Channel, killing all aboard. The unit is Paul's. His name is absent from the casualty list, but one soldier remains unidentified. Marta touches the dog tags around her neck, knowing Paul never got replacements. She sees his face in a unit photograph and collapses.
After weeks of grief, Marta encounters Simon, who renews his job offer at the Foreign Office. She suppresses a growing suspicion of pregnancy. Simon courts her and proposes after just four weeks. Marta accepts without passion. Seven months into the marriage, she gives birth to a daughter, Rachel. Marta knows the baby is Paul's, but Simon accepts the early arrival without question. Married life proves lonely and emotionally cold.
Two and a half years after the war, during a classified briefing, Marta learns a Soviet mole has been compromising British intelligence. The only way to identify the traitor is to obtain a coded cipher, a key for decrypting a list of Soviet agents, believed to be in the hands of Jan Marcelitis, a legendary anticommunist operative. When a Prague contact named Marek Andek is mentioned, Marta recognizes him as a former resistance leader from Kraków. She reveals her resistance past for the first time, stunning Simon, and volunteers to travel to Prague.
In Prague, Marta contacts Marek, who reluctantly arranges a meeting with Marcelitis. At the rendezvous, Emma appears instead; she married Marek after Jacob died of fever in Slovakia. Emma explains that Marek fears surveillance and has arranged a midnight meeting with Marcelitis on the Charles Bridge. That evening, communists seize power in a coup. At midnight, an imposter attacks Marta with a knife. She escapes but finds her embassy driver, Renata, dead. Emma reveals Marek was arrested and broke under interrogation, compromising the meeting. She tells Marta that Marcelitis has likely fled to Berlin. Emma gives Marta plain clothes to help her blend in, and they say goodbye.
On a train toward Germany, Marta's attacker reappears. She leaps from the moving train. As the man pursues her into a forest, she fires her pistol. A second shot rings out, and he falls dead. A figure emerges from the trees.
It is Paul. He survived the Channel crash as the sole survivor and was recruited by American intelligence under a new identity. When he learned Marta was the operative being tracked, he volunteered for the assignment. Together they reach Berlin, where Marcelitis has just been arrested. They break Marcelitis out of a police station and are stunned to discover Jan is a woman. In a hidden wine cellar, Marta presents the intelligence package, and Jan agrees to exchange the cipher. Paul reveals he once came to find Marta after the crash but saw her pregnant in her garden and left, believing she had moved on.
Jan returns with the cipher and arranges their escape on a freighter. At the port, guards discover Paul, but both manage to board the ship. Paul collapses from a gunshot wound. In the cargo hold, Marta tends to him and tells him Rachel is his daughter.
Back in England, Paul calls Marta. They confess their love, but she tells him they cannot continue. Then she overhears Simon on the phone arranging a flight from Luton Airport. She breaks into his locked desk and discovers Russian-language telegrams proving he is a Soviet agent who compromised her intelligence contacts. She finds Rachel's crib empty: Simon drugged a chocolate he gave her to incapacitate her and take the child. She calls Paul and races to the airport.
Simon admits he was recruited as a communist agent at Cambridge long before meeting Marta. He reveals that Dava was also a Soviet operative planted in the displaced persons camp. Marta realizes Dava killed Rose to create the visa that brought Marta to England, and that Simon orchestrated Paul's plane crash to isolate her. Their entire marriage was designed to exploit Marta's resistance connections. Paul arrives and fights Simon. Inside the plane, Dava holds Marta at gunpoint, but Marta disarms her. When Simon pursues Marta across the tarmac, Dava shoots him dead before collapsing.
In the epilogue, Marta, Paul, and Rachel stand on the deck of an ocean liner bound for America. Paul proposes again with a diamond ring, and Marta accepts. She reflects on all she has survived, acknowledging that the years with Simon are part of her story but will not define it. They go below deck together as the ship carries them toward a new beginning.