In Paris, aging CIA agent Cross meets with his protégé, assassin Jean Laurier to arrange a hit on Arab leader Salem Zim and make it appear that he was killed by a left-leaning country. After the successful assassination, the men board a Washington D.C.-bound plane, where Cross explains that although Zim had America’s backing, it was politically more advantageous that he be viewed as a victim of a country hostile to U. S. interests. Upon arrival in America, Laurier is met by his sister Anne and Cross by his wife Sarah. Although pleased to be reunited with Sarah, Cross remains wary about his homecoming and the next morning confirms that agents are watching him from a vacationing neighbor’s house. Meanwhile, agent Filchock meets with Laurier, known to the agency by his code name Scorpio, and takes him to meet chief McLeod. When McLeod demands to know why Laurier did not kill Cross in Paris as contracted, Laurier remains evasive. Despite the surveillance, Cross heads off to the agency to make his report, but when two agents pursue him aggressively, he turns to old friend Pick for assistance in leaving the country immediately. After Pick contacts Sarah to tell her that Cross is now on the run, he provides identity papers and a ticket for Cross to go to Vienna via Canada disguised as a black priest. Meanwhile, McLeod arranges to have Laurier, who is with his longtime girl friend Susan, arrested on a false drug charge to force him to work with the agency to locate and eliminate Cross. Laurier tells McLeod that he did not kill Cross because Cross hired him to kill Zim before McLeod put out a contract on Cross. The assassin then reveals that he has sensitive information about the agency provided by Cross which would make him dangerous should McLeod attempt to take him to court on the phony drug charge. Laurier then demands Cross’s position in the agency as well as an additional fee of $25,000 to kill him. After McLeod reluctantly agrees, Laurier demands to know why the agency is after Cross and McLeod discloses that Cross is a double agent for the Soviets. Although dubious, Laurier suspects that Cross will seek out another old associate, KGB agent Sergei Zharkov, and asks for McLeod’s assistance in questioning a former Soviet spy currently under American protection. Learning that Zharkov has an apartment in Vienna, Laurier bids farewell to Susan and, with the agency’s authority, travels to Vienna. In Vienna, Zharkov provides Cross with an apartment and confirms Cross’s suspicion that the agency wants to kill him. Cross confesses that he is not planning to defect to the other side but rather wants to retire from the espionage business for good and wants Sarah transported over as soon as possible. Over drinks, both men lament that the younger generation of agents on either side have no political loyalties or beliefs and are intrigued only by the “game” of spying. Upon arriving in Vienna, Laurier is met by agent Mitchell, but scoffs at his inability to confirm Cross’s whereabouts. Insisting that his association with Cross has taught him how to think like him, Laurier deduces Cross will attempt to bring Sarah over. The next day, Cross contacts Max Lang, a former World War II resistance fighter whom Cross rescued from a concentration camp, to arrange for Sarah to travel to Rome. After Mitchell assigns assistant agents Novins and Dor to help Laurier, the Frenchman learns that the agents’ Soviet contacts insist there has been no contact with Cross for more than twenty years and begins to suspect McLeod’s explanations about Cross. Upon receiving a covert message from Cross, Laurier meets him that night at a park where Cross insists he has never sold information to the Soviets, but admits he is friendly with Zharkov who, like him, was once a dedicated anti-fascist. Warning Laurier that McLeod has also ordered Laurier’s termination, Cross explains he has freely provided Laurier with information on the agency in order for him to have bargaining power with them. When Norvin and Dor unexpectedly arrive, Cross flees while Laurier returns to his hotel. Although angered that Laurier allowed Cross to escape, Mitchell plays him a recording of Max contacting Sarah by phone, but is surprised when Laurier already has complete information on Max. In Washington, Filchock shows McLeod surveillance footage of Sarah running several innocuous errands that he believes imply she is about to flee the country. Hoping to frighten Sarah, McLeod orders a phony robbery on her home. In Vienna, on Mitchell’s orders, Novins and Dor search Max’s apartment and when the older man arrives they beat him in vain for information on Cross. Afterward while the men consult with Laurier in a car, Cross arrives to meet Max and is forced to shoot Dor while escaping. Laurier and Novins pursue Cross to a construction site where Novins sets off an explosives pile before Cross hurls him to his death from a catwalk. When the authorities arrive to quell the explosion, both Cross and Laurier depart the scene in opposite directions. The next night, Sarah is at neighbors Helen and Heck Thomas’ house at a party, but distracted, she leaves early. Heck, who is a CIA agent, grows alarmed when he discovers her absence, as he knows the phony robbery is in progress. When Sarah notices movement in her home, she gets a pistol from the garage and, confronting the men, shoots one, who fires back and kills her. In Vienna, after Zharkov meets with his superior Malkin who orders him to take Cross to Moscow, he advises Cross to flee as both sides are closing in on him. After arranging for a boat to take Cross out of Vienna, however, Zharkov learns of Sarah’s death and finds Cross on the boat to inform him. Convinced that Cross is not a double agent and will return to Washington to seek revenge for Sarah’s death, Laurier returns there, but McLeod tells him they have received information that Cross is in Moscow. Unknown to the CIA, Zharkov has blackmailed Malkin into letting Cross go. Cross promptly returns to Washington where, with Pick, he learns that McLeod was ultimately behind Sarah’s murder. The day after Sarah’s funeral, Cross shoots McLeod in his limousine and evades detection. Disgusted by the agency’s methods, Laurier decides to return to Paris and makes plans for Susan to join him there. Having replaced McLeod, Filchock orders Laurier brought to the agency where he insists that the assassin fulfill his contract on Cross. When Laurier maintains that Cross is not a traitor, Filchock shows him several films that purport to show Cross in questionable situations with various communist agents. Upon seeing the recent footage of Sarah, Laurier is startled to recognize Susan in a shot and realizes that she has been working for Cross. That evening after searching Susan’s apartment, Laurier trails her to a garage where she meets and provides Cross with money. Furious, Laurier shoots her then turns against Cross, who cautions him that the agency will never allow him to live. Defiantly, Laurier shoots Cross whose last words are that there is no good or bad and that the object isn’t winning or losing but staying in the game. Unmoved, Laurier departs and while pausing to pet a stray cat, is shot down by the agency’s waiting assassin.