In the present day, a quiet stranger moves into a cottage in the Cornish village of Port Navas. He becomes the subject of intense surveillance by Timothy Peel, an 11-year-old boy who has recently moved nearby with his mother and her hostile lover, Derek. Peel observes the stranger’s meticulous work restoring a vintage MG roadster and an old ketch sailboat.

After a large crate is delivered, the stranger begins working all night in his upstairs studio under powerful white lights. One evening, Peel investigates and is caught by Derek, who strikes him. The stranger intervenes, chiding Derek for his harshness. Frustrated, Peel later breaks into the stranger’s cottage and discovers a professional art restoration studio containing two valuable paintings, one a Rembrandt. The stranger catches him but, instead of being angry, explains his profession and offers Peel a job as a helper and watchman. He then invites the boy sailing, but does not answer when Peel asks for his name.

Emily Parker, a heartbroken American in Paris, is introduced to a mysterious man named René by her new friend, Leila Khalifa. Emily and René begin a passionate affair, but he soon becomes secretive and distant. After confronting him, he takes her to the Pont Alexandre III bridge and gives her an expensive bracelet. The romantic moment is interrupted by a staged car crash that halts traffic, trapping a limousine carrying Israeli Ambassador Zev Eliyahu. René reveals his true nature by pulling a submachine gun from his backpack and leading a coordinated attack. He tosses the backpack beneath the limousine and waits for it to detonate, then walks forward and shoots the survivors, killing Eliyahu, his wife Hannah, and their bodyguards. When a horrified Emily confronts him, René shoots her and the force of the bullets drives her over the parapet into the Seine, where she drowns.

Ari Shamron, a legendary Israeli spymaster recently brought back from retirement to lead the Office, the inhouse name for the Israeli intelligence service known more commonly as Mossad. Shamron rarely sleeps; he receives news of an ambassador’s assassination in Paris. After traveling to his Tel Aviv headquarters, Shamron analyzes television reports of the attack. Based on the meticulous planning, the killer’s calm ruthlessness, and the presence of a female companion used as cover, Shamron deduces the perpetrator is a notorious terrorist named Tariq al-Hourani. He then meets with Israel’s prime minister, revealing that the slain ambassador was a personal friend and former Office colleague. Shamron tells the prime minister that he has a long-term intelligence source within Tariq’s organization. The prime minister grants Shamron authorization to find and eliminate Tariq, demanding a clean operation with no ties back to Israel. To carry out this covert mission, Shamron decides he must recruit Gabriel Allon, a highly capable former operative now living in retirement in England.

After a delayed ferry crossing from Turkey, the assassin Tariq arrives on the Greek island of Samos. He has spent the five days since the Paris assassination traveling across Europe, changing identities and seducing women. He reflects on his past in a refugee camp, which fuels both his hatred for his enemies and a compulsion to be with women during operations. At a secluded villa, he finds a messenger named Achmed waiting for him. Achmed provides a train ticket and a message from a man named Kemel, who is demanding an urgent face-to-face meeting on a train to Prague. Annoyed by the security risk of a direct meeting, Tariq becomes furious when Achmed admits to carelessly loitering in the local village, potentially drawing attention. Deeming Achmed a liability, Tariq takes the train ticket and then shoots and kills Achmed. His plans for recuperation on the island ruined, Tariq leaves the villa immediately.

Uzi Navot secretly delivers a surveillance videotape from the Musée d’Orsay to Ari Shamron in Tel Aviv. Shamron obsessively re-watches the tape, dismissing Navot’s observations about a suspicious phone call and instead fixating on the type of food—tandoori chicken—being served by a waiter. A frustrated Navot visits his former lover, Bella, then goes in search of tandoori chicken, apparently trying to understand why Shamron focused on it. Meanwhile, Shamron’s intense pressure on his staff yields two breakthroughs. A researcher identifies the waiter as Mohammed Azziz, a known associate of the terrorist Tariq, officially linking him to the attack. Shortly after, news arrives of a Palestinian’s murder in a Greek villa that was rented by a fictitious Englishman named Patrick Reynolds. Following a final, brief meeting with a newly determined Navot, Shamron prepares to go into the field under an alias. He dismisses his bodyguard’s concerns and departs alone on his mission.

Kemel Azouri, the chief of sales for Schloss Pharmaceuticals, lives a secret double life. Publicly a successful executive, he is secretly the chief of operations and planning for the terrorist Tariq al-Hourani, using his company’s resources to move weapons and money. After a board meeting in Zürich, Azouri withdraws a large sum of cash from a personal numbered account and boards a train, pretending to be on a business trip. Onboard, he has a clandestine meeting with Tariq, who is disguised as an American tourist. Tariq admits to killing the messenger Azouri sent to him. Azouri gives Tariq the cash and briefs him on an upcoming operation in Amsterdam. He then reveals critical intelligence: Ari Shamron and Israeli intelligence know Tariq was behind the recent Paris attack, and the prime minister has authorized his assassination. The agent assigned to the mission, he says, is one of Tariq’s old acquaintances.

Ari Shamron, disguised as a German art buyer named Rudolf Heller, visits the financially troubled London gallery of Julian Isherwood to find Gabriel Allon. Isherwood initially refuses to help, stating he needs Gabriel more than Shamron does. Over a tense lunch, Isherwood, who is revealed to be a sayan (a civilian helper for Mossad), explains his predicament. He has acquired a damaged but valuable painting that Gabriel’s X-ray and infrared analysis confirmed as a lost masterpiece by Francesco Vecellio. Isherwood’s financial survival depends on Gabriel, one of the world’s few qualified restorers, preparing the painting for a critical sale. Isherwood also insists Gabriel is finished with his old life. Shamron counters by offering to arrange an anonymous financial backer to keep Isherwood’s gallery solvent until the painting is sold. In exchange, Isherwood must reveal Gabriel’s location. The chapter ends with Isherwood appearing ready to accept the deal.

An old man arrives looking for the stranger, Gabriel Allon. The boy, Peel, warns Gabriel, who recognizes his visitor as Ari Shamron, his former intelligence chief. Shamron asks Gabriel to return to service to hunt down the professional terrorists responsible for a recent deadly attack in Paris. Gabriel refuses, arguing revenge is a pointless cycle. Shamron reveals that Tariq orchestrated the attack and presses Gabriel by invoking the Vienna bombing that targeted his family, telling Gabriel that helping take down Tariq might allow him to forgive himself. He wants Gabriel to run a clandestine surveillance operation in London on one of Tariq’s known associates.

Haunted by the memory of his family and Leah’s plea before the bombing that he leave the Office, Gabriel wrestles with the decision. After reviewing a file on the target, Gabriel calls Shamron. Using coded language, he accepts the mission, demanding operational autonomy and a high fee. He then prepares his boat for a long absence and drives away from Port Navas.

Shamron travels to London to meet Benjamin Stone, the bombastic owner of Looking Glass Communications and the Office’s most valuable sayan. Stone has long provided Shamron with media cover, propaganda placement, and covert funding funneled through shell companies. Despite Stone’s complaints about Looking Glass’s mounting financial troubles and his demands that Shamron pressure Israeli investors to forgive his debts and supply him with exclusive stories, he agrees to transfer $500,000 into a Bahamian account under the cover of a struggling shipping company called Carlton Limited. Stone flatly refuses to make a bridge loan to Julian Isherwood’s art dealership, no matter how personally Shamron frames the request.

The following morning, Shamron meets Gabriel in Hampstead Heath and confirms the funds are in his Geneva account. He then lays out strict operational constraints: Because Shamron’s rival Lev controls London Station, Gabriel is barred from using its staff, safehouses, secure cables, or diplomatic pouches except through a trusted Foreign Ministry contact. Shamron provides three loyal London contacts, a routed Oslo phone number, and instructs that any required face-to-face meetings occur in Paris using sites and protocols from the old Black September operation. Back in Israel, Shamron briefs the prime minister and reveals a complication: Stone is in financial ruin and could expose their operations if he goes down. Shamron doubts blackmail will work, and the prime minister authorizes him to deal with Stone as he sees fit. With the communication and financial framework established, Gabriel tells Shamron to leave the United Kingdom immediately, then walks away.

Julian Isherwood meets with a rival art dealer, Oliver Dimbleby, who outlines Isherwood’s dire financial situation. Dimbleby confesses that a drunken acquaintance smashed the window of their main competitor, Giles Pittaway. Dimbleby then offers to buy out Isherwood’s gallery. Isherwood furiously rejects the offer, realizing his only hope for survival is for Gabriel to finish restoring the valuable Vecellio painting. Unable to reach Gabriel by phone, Isherwood learns from an art supply shop that Gabriel has canceled all future orders. He drives to Gabriel’s cottage in Cornwall and finds it empty. A local boy, Peel, confirms that a “bald man who walked like a soldier” took Gabriel away, which Isherwood knows means Shamron has him (124).