Paul Tanner, a Naval Academy graduate and Department of Justice attorney, and Chelsea Tanner (née Clayburn), an art appraiser fluent in French, arrive in Paris for their honeymoon after their wedding in Annapolis. A mole inside their Left Bank hotel identifies them as targets, and the kidnappers use Chelsea's detailed social media postings to track their movements. On the fifth day, the couple hires a private car driven by Malik for a day trip to the D-Day beaches in Normandy. During lunch in Bayeux, a staged bicycle crash distracts Malik while a young woman slips a sedative into his water, knocking him unconscious. A man calling himself Laurent, disguised in a chauffeur's uniform, takes the car and picks up Paul and Chelsea, claiming Malik had a family emergency. Laurent releases nitrous oxide into the rear seat, rendering both unconscious, then injects them with ketamine.
Chelsea awakens hooded and bound in a pitch-black room. An unseen man with accented English tells her to cooperate if she wants to see Paul again. The captors force her to record proof-of-life videos. That evening, Chelsea's mother, Justine Clayburn, receives a text directing her to an encrypted email containing a video of Chelsea under armed guard, a $2 million ransom demand, and a warning not to contact law enforcement. Justine and her husband, Dr. Lowell Clayburn, a wealthy orthopedic surgeon, are paralyzed with fear. Their son Sam takes charge, advising against calling the FBI. Paul's parents, Fritz and Linzy Tanner, receive their own video of Paul, his face beaten and bloody, along with a separate $2 million demand.
Lowell liquidates investments and flies to Paris. The Tanners face a far more desperate situation: They must sell their family home in Old Town Alexandria at a steep loss and drain every account to raise funds, and the Clayburns loan them $250,000 to cover the remaining gap. In Chantilly, north of Paris, Chelsea is released after the Clayburns wire their $2 million and reunites with Lowell in a church. She insists she will not leave France without Paul. When the Tanners wire their ransom, Chelsea is told to wait in the Church of Saint-Sulpice in Paris, where Paul will supposedly arrive at four o'clock. She waits as the bells ring at four, then five. Paul never comes. Devastated, Chelsea flies home with her father.
At Dulles Airport, FBI agents, including Agent Lon Dyer, meet the Clayburns and escort them to a private office where both families are gathered. Dyer becomes the families' primary contact. Chelsea undergoes a lengthy debriefing, and the FBI establishes a cover story that Paul fell ill with food poisoning and remains hospitalized in Paris. In France, FBI Special Agent Pascal Goff, stationed at the U.S. embassy, coordinates with Jean-Pierre Chalamet of the DGSI, the French equivalent of the FBI, but the investigation produces almost nothing.
Paul has been smuggled out of France in a metal shipping crate, heavily sedated, and delivered to a fishing village on the Algerian coast. He is transported deep into the desert to a hidden compound run by Nabeed, a 35-year-old Algerian florist. Nabeed was captured by American soldiers in Afghanistan, tortured at Abu Ghraib prison and a CIA black site in Poland, then held at Guantánamo Bay for eight years without being charged. His younger brother was killed by American soldiers at Kandahar prison. Paul endures systematic torture at the compound, which Nabeed has named "Camp Echo" after Guantánamo: beatings, waterboarding, sleep deprivation, and near-starvation. Nabeed reveals his motivations and tells Paul that two other Americans are also held there. A young guard Paul nicknames Alfie begins visiting for English lessons and secretly bringing Paul extra food, forming an unlikely bond.
FBI Director Huff Norton learns this is the third such kidnapping. Alan Stockman, a veteran of the Judge Advocate General's Corps (JAG Corps), the U.S. military's legal branch, was abducted near Bordeaux three years earlier, and Jason Snyder, also a former JAG officer and federal prosecutor, was taken near Giverny eleven months prior. All three men share military backgrounds and JAG Corps service. Norton decides the matter belongs to the CIA.
The CIA devises a covert operation. Rae Claire Russo, a CIA officer embedded at a publishing house in Washington, and her colleague Webb McBride recruit Stuart Nash, a 31-year-old assistant federal prosecutor from Charlotte. Nash's key asset is his connection to Guantánamo Bay, where he served on a prosecution team, making him an irresistible target for kidnappers motivated by anti-American military grievances. The plan is to stage a fake honeymoon in Paris to lure the gang, then track Nash to the hostages' location. Nash agrees out of a sense of duty. He relocates to Washington and begins an elaborate courtship with Rae Claire. They undergo hostile-environment training at Camp Peary, the CIA's covert facility known as "The Farm." CIA technicians implant transmitter bugs in two of Nash's molars that activate when he clicks his teeth together, sending signals detectable by surveillance drones and satellites.
In November, Cully Pratt, the founder of Clemency International, a Dublin-based human rights nonprofit, contacts the authorities claiming to represent the hostage-takers. He delivers a demand: $100 million for all three hostages, with executions to follow if terms are rejected. Pratt leaks the story to
The Guardian, and the resulting publicity devastates the families and intensifies pressure on the government.
Nash and Rae Claire marry in a small ceremony in Georgetown on December 10 and fly to Paris, checking into a Left Bank hotel while posting their itinerary on social media. Their relationship, initially professional, becomes genuinely intimate. A CIA team monitors them from nearby, but Nabeed's operatives have taken the adjacent room. At midnight, nitrous oxide is released from canisters hidden under the bed. The operatives enter through the adjoining door, inject both with ketamine, scrub the room, and smuggle the unconscious couple out through the service elevator. The CIA discovers them missing only the next morning.
Rae Claire is held near Dijon. Nash is taken to Marseille, waterboarded, and interrogated about Guantánamo. During the session, he clicks his molars, sending a signal detected near Marseille. He is loaded into a crate and shipped by boat across the Mediterranean. Through Pratt, the kidnappers escalate their demand to $200 million for all five hostages, threatening to begin executions with Rae Claire. The president authorizes payment. Simultaneously, signals from Nash's transmitters are tracked to the Algerian desert. SEAL Team 7, a U.S. Navy special-operations unit staged on an aircraft carrier off Morocco, parachutes into the desert but finds Camp Echo abandoned.
Meanwhile, Alfie drives the four American hostages into the desert, cuts their bonds, gives a half-salute, and drives away. Nash identifies incoming French helicopters as friendly, revealing he has been tracked. The SEALs extract all four men and fly them to a U.S. base near Algiers.
Dyer, the families' FBI contact, calls Chelsea with the news that Paul has been rescued. The three original hostages are transferred to Sicily for medical care, and Chelsea reaches Paul by phone. The following morning, Rae Claire is released in a village near Marseille. Nabeed, now traveling under a Turkish passport, retreats with his team to a villa on a Turkish island in the Aegean Sea, hoping to disappear with his fortune.
Nash and Rae Claire reunite in Washington. Their relationship, which began as a CIA fabrication, has become unexpectedly genuine. Nash proposes they take a real honeymoon over Christmas in Barbados to decide whether their marriage should continue. Rae Claire agrees, and he offers to book the flights.