Charles Heller is a CIA cryptographer who spends his days restoring an old Cessna as a gift for his wife, Sarah, who is about to depart on a business trip to London. Within the CIA's Decryption and Analysis division, Heller has formed a uneasy circle of contacts, including a field operative nicknamed “The Bear” and an anonymous source known as “Inquiline.” When Inquiline’s classified files surface, they reveal that the Special Activities Center Director, [Alex Moore] (noted in the files), has been disguising politically charged drone strikes as suicide bombings. The bombshell hits hard when CIA Director Samantha O'Brien informs Heller that Sarah was killed in a terrorist attack.
Driven by grief and a fierce need for truth, Heller begins to connect the dots himself. He reconstructs the sequence of events: after an arms deal collapses, four gunmen abduct Sarah and others and kill her before slipping away. He identifies the four suspects—Mishka Blazhic, Ellish, the Armenian intelligence officer Gretchen, and the elusive Horst Schiller—though Moore and his deputy, Caleb Horowitz, insist their mission is to dismantle Schiller’s vast network. Heller presses his case, exposing his own orders which caused numerous civilian and allied casualties, and demands the resources and training he believes he should have to pursue the four assailants personally.
With the agency’s blessing, Heller is sent to Camp Peary to train under Colonel Henderson. He discovers a surprising talent for bomb construction, but Henderson doubts that Heller can ever become a killer. Back at the office, Moore and Horowitz rummage through Heller’s personal files, including a CD hidden in a jukebox, and realize he had been bluffing about a broad network. Henderson is ordered to eliminate him, and the hunt is on as Heller goes on the run.
Heller’s first break comes in Paris, where he tracks down Gretchen. He discovers her assignment at an allergy clinic and, armed with a pistol, confronts her after a tense lock-picking sequence. Haunted by the memory of Sarah, Heller traps Gretchen inside an allergy clinic’s hypobaric chamber and floods the room with pollen. He demands to know Schiller’s whereabouts, but his humanity wins out—he cannot allow Gretchen to die and releases her. Gretchen makes it to the street, only to be struck fatally by a van.
Gretchen’s phone helps Heller slip away to Marseille, where Henderson corners him in a bar. An explosion in the restroom buys Heller time to escape, and he calls in Inquiline for help. Inquiline reveals herself as Davies, the Russian widow of a murdered ex-KGB officer who has infiltrated the CIA’s information network. Davies leads Heller to Madrid where the trail points toward Blazhic’s operation aboard a luxury hotel hotel.
Meanwhile, Samantha, wary of Moore’s judgment, sends her own operative to safeguard Heller. In Madrid, Heller faces Blazhic in a rooftop confrontation by a hotel pool. Blazhic has rigged scuba gear to decompress the air inside the pool’s glass, and when Blazhic refuses to cooperate, Heller shatters the glass and Blazhic falls to his death. Henderson nearly corners Heller again, but a struggle leads to Henderson being wounded and the CIA operative on the run once more. Caleb, tracking Davies, discovers the Russian connection and arranges a response from Istanbul, where a Russian FSB unit moves in. Davies is killed while fleeing with Heller.
Heller continues to chase the shadows, this time tracking Ellish to Romania under the cover of a missile deal. A cleverly set trap forces Ellish to reveal that Schiller operates from a ship in the Baltic Sea. Heller retrieves Ellish’s phone and leaves him to die in the explosion, then heads to Primorsk to spy on Schiller’s operation. The Bear, a nickname that hints at his past, confronts him, but Heller refuses to end his vendetta.
Captured at last, Heller is brought aboard Schiller’s ship to confront the man who killed Sarah. Schiller offers a loaded gun and a chance for instant vengeance, but Heller has other plans. He reveals that he has hacked the ship’s systems, steering it toward the Gulf of Finland where Schiller is detained by Finnish police and Interpol. Moore and Caleb are exposed for their unsanctioned actions, and Samantha publicizes a purge within the agency to root out bad actors. After a visit from a recovered Henderson, Heller completes the restoration of his plane and climbs into the cockpit for a long-awaited flight, finally finding some measure of peace in the open sky.
