During the Korean War, the Soviets capture a U.S. platoon and take them to Manchuria in Communist China. Some days later, all but two of the soldiers return to the U.S. lines and Staff Sergeant Raymond Shaw (Laurence Harvey) is credited with saving their lives in combat by his fellow platoon members. Upon the recommendation of the platoon's commander, Captain Bennett Marco (Frank Sinatra), Raymond is awarded the Medal of Honor. When asked to describe him, Marco and the other soldiers automatically respond, "Raymond Shaw is the kindest, bravest, warmest, most wonderful human being I've ever known in my life." Deep down, however, they know that Shaw is a cold, sad, unsympathetic loner.
Following his return to America, Marco, who has since been promoted to major, suffers from a recurring nightmare in which a hypnotized Shaw blithely and brutally murders the two missing soldiers before an assembly of military brass from the Communist nations, during a practical demonstration of a revolutionary brainwashing technique. Marco wants to investigate, but has no solid evidence to back his claims and thus receives no support from Army Intelligence. However, Marco learns that another soldier from the platoon, Allen Melvin (James Edwards), has had the same nightmare. When Melvin and Marco separately identify some of the men in the dream as leading figures in communist governments, Army Intelligence agrees to help Marco investigate.




Sgt. Shaw (Harvey, left) meets Major Marco (Sinatra, right), after having jumped into a lake in Central Park, New York.
Meanwhile, Shaw's mother, Mrs. Eleanor Iselin (Angela Lansbury), drives the political career of her husband and Shaw's stepfather, Senator John Yerkes Iselin (James Gregory), a McCarthy-like demagogue who is widely dismissed as a fool. Senator Iselin raises his political profile when he claims that varying numbers of communists work within the Department of Defense. However, unknown to Raymond, Mrs. Iselin herself is actually a Communist agent with a plan intended to secure the presidency under Communist influence.
Mrs. Iselin is the American operator responsible for controlling Raymond, who was "brainwashed" in Manchuria to be an unwitting assassin whose programming is triggered by a Queen of Diamonds playing card. When he sees it, he will blindly obey the next suggestion or order given to him and never have any memories of those actions. It is revealed that Shaw's heroism was a "false memory" implanted in the platoon during their brainwashing, and that the actions for which Shaw was awarded his Medal of Honor never took place. Shaw's conditioning is reinforced by Chunjin (Henry Silva), a North Korean agent who supervises him under the guise of his cook and houseboy. When Marco visits Shaw's apartment, he becomes suspicious of the Korean and they engage in a fight using karate techniques.
Raymond briefly finds happiness when he rekindles a youthful romance with Jocelyn Jordan (Leslie Parrish), the daughter of Senator Thomas Jordan (John McGiver), one of his stepfather's political rivals. Mrs. Iselin had previously broken up the relationship, but now facilitates the couple's reunion as part of her scheme to garner Jordan's support for her husband's bid for Vice President. Jocelyn, wearing a Queen of Diamonds costume, inadvertently triggers Raymond's programming at a costume party and elopes with him. Although pleased with the match, Jordan makes it clear that he will block Senator Iselin's nomination. Mrs. Iselin triggers Raymond and sends him to kill Jordan; he also shoots Jocelyn when she happens upon the scene. Afterwards, Raymond has no knowledge of his actions and is grief-stricken when he learns of the murders.
After discovering the card's role in Raymond's conditioning, Marco uses a forced deck to get the full story. He then verbally drills into Raymond the suggestion or affirmation that the Queen of Diamonds no longer has any power over him. Mrs. Iselin primes her son to assassinate their party's presidential nominee at the nomination convention so that Senator Iselin, as the vice-presidential candidate, will become the nominee by default and be elected with emergency powers that, in Mrs. Iselin's words, "will make martial law seem like anarchy." Mrs. Iselin tells Raymond that she did not know that he was to be selected by the Communists, but vows that once in power she will "grind them into the dirt" in revenge.
Marco's attempt to free Raymond from his brainwashing appears to have failed, and Raymond enters Madison Square Garden disguised as a priest and takes position to carry out the assassination. Marco and his supervisor, Colonel Milt (Douglas Henderson), arrive at the convention to stop him. As the nominee makes his speech, Raymond, instead of assassinating him, shoots his stepfather and then his mother with the sniper rifle she gave him. He then commits suicide in front of Marco while wearing his Medal of Honor. Marco, in the film's final scene, reads the (real) Medal of Honor citations of Daniel R. Edwards and Nelson M. Holderman, before voicing a fictional citation for Raymond's genuine act of heroism in stopping the Iselins.
Who is Shaw's stepfather?
Senator John Yerkes Iselin