Martin Harris (Liam Neeson) and his wife Liz (January Jones) arrive in Berlin for an important biotechnology conference, where he is set to present a paper. However, chaos ensues when Martin realizes that he left the briefcase containing their passports at the airport. While Liz checks in at their hotel, he rushes off to retrieve it. Unfortunately, a sudden truck accident sends his cab plunging into the river. Just in the nick of time, he is rescued by Gina, a cab driver who vanishes as the authorities arrive.
Following a four-day coma, Martin wakes up with fragmented memories and a sense of urgency to attend the conference. He checks out of the hospital, intent on reuniting with Liz at the hotel. To his shock, she claims not to recognize him and introduces another man, Martin B (Aidan Quinn), as her husband. Confused and desperate, Martin meanders through Berlin, trying to piece together what has gone wrong.
His search leads him to Gina, who is hesitantly working multiple jobs as an illegal immigrant. Fearing deportation, she initially resists helping him. Martin then tries to meet with Professor Bressler (Sebastian Koch), with whom he was supposed to collaborate on groundbreaking advancements in food production. Yet, upon arrival, he finds Martin B already there, leading to an altercation that gets him removed by the police.
Feeling increasingly desperate, Martin returns to the hospital for further evaluations and learns from a nurse about a private detective, Ernst Jurgen ([Bruno Ganz]). Jurgen, a former Stasi officer, believes Martin's implausible tale and advises him to reach out to Gina again. After finding her, he gives her a watch that Liz gifted him, asking for her help. But their refuge is short-lived when a hit man confronts them; Gina manages to save Martin by eliminating the assailant with his own poison. They narrowly escape from further danger by seeking refuge in a nearby discotheque.
United with Jurgen once more, they obtain valuable intelligence regarding Martin's situation, including the whereabouts of security footage from the airport. Martin follows Liz to a photography exhibition where she confides her torment—she’s being coerced to betray him, yet she still loves him and awaits him at the airport. Just as Martin makes sense of everything, trouble arises again with the appearance of Martin B and another hit man, forcing Martin to flee with Gina once more.
Meanwhile, Rodney Cole (Frank Langella) arrives at Jurgen's office, but his true intentions become apparent when Jurgen chooses to take cyanide rather than disclose information concerning him. Martin and Gina then find the vital briefcase containing their passports and a windfall of euros. Deciding to leave for the airport, Gina parts ways with Martin, only to witness him being abducted by the second hit man, with Cole revealing himself to be a government assassin using the name "Martin Harris" as a cover. When Martin regained consciousness after the accident, he believed this false narrative, prompting the need for Martin B to complete their mission.
In a climactic moment, Gina rescues Martin from imminent death, resulting in a chaotic confrontation that ends with a dramatic crash. Now fully remembering the events that led to this chaotic moment, Martin recalls plotting a bomb with Liz to take out Bressler in a way that could be blamed on others. Racing against time, Martin and Gina rush to infiltrate the hotel where Liz prepares to detonate the bomb. In a heartbreaking sequence, Liz fails in her attempt to disarm it, leading to a catastrophic explosion.
The next day culminates with Bressler and Prince Shada unveiling their new agricultural contribution aimed at combatting world hunger, while Martin and Gina, under assumed identities, prepare to leave Berlin together as Henry and Claudia Taylor.
