The caper concerns a man who hires nuclear power plant specialists. Seems he's bee selling low-grade intelligence about U.S. nuclear power plants "to the other side."The cad plans to turn double-agent. But he is terminated with extreme prejudice at a zoo where U.S. agents are waiting for him to meet "the other side." The doom is done with a four-pointed metal weapon, "the death star," a device Hunter recognizes as the trademark of a years-ago foe named "Bluebird," an ace Communist intelligence agent he hates.
By subjecting one of their own people to plastic surgery and re-education, the Reds create an exact replica of secret agent Jim Hunter (James Franciscus) for the purpose of using the false Hunter to get the true Hunter out of their hair. Their plan is to use the false Hunter to lure Baker (Ralph Bellamy), the US. Intelligence Kingpin who is Hunter's supervisor, into a trap and to kill him before witnesses, thereby framing the true Hunter for the murder of his boss. Proceeding with the first phase of the plan, the Soviet agents kidnap Hunter in order to isolate him temporarily. Then they palm off the false Hunter on Marty Shaw (Linda Evans), Hunter's lover and fellow secret agent, tensely waiting to see if the imposter will pass this most meticulous test.
Using an experimental mind-altering technique, Russian agents program Marty Shaw to assassinate her uncle, US. Admiral Carleton Young, in a plot that also calls for the murder of James Hunter. William Windom guest stars as one of the Soviets. While Marty is unaware she has been subjected to psychological tampering, Hunter suspects, "something" has happened to her, though he is mystified as to what, by whom, and to what purpose. As he tries to find evidence that can reveal what is going on, the Red agents make their final preparations for the day on which Marty is to do their will and Hunter is to die.
