Dan goes into a closed pawnshop and picks up his briefing on Carl Wilson, a special U.S. envoy working on an agreement between the U.S. and a neutral country. Enemy agent Peter Kiri has kidnapped Wilson and replaced him with an imposter, Gort, and plans to sabotage the agreement. The IMF must rescue Wilson and put Kiri out of action.
Dan assembles the usual team, plus Dr. Ira Drake, a neuropsychologist. The team reviews a picture of the Wilson imposter and concludes Dan will have to disguise himself as Wilson. Piri has taken over Wilson's staff and hidden the envoy somewhere else. Rollin makes Dan up to look like Wilson while Barney tests his sound equipment and he and Willy set up a special chamber.
The disguised Gort and Kiri go over their plan while Cinnamon shows up as Wilson's house as his niece. Pretending to be Wilson's assistant, Piri greets her while Willy brings in her luggage… with Dan-as-Wilson inside. Willy knocks out Gort while Dan takes over and smoothly continues his conversation with Cinnamon to fool Piri who is listening in. Cinnamon checks into a hotel, unaware that they've left Gort's cigarette holder behind. Once she's gone, Dan lights up with a cigarette sans holder and Piri picks up on it.
Cinnamon and Willy take Gort to a warehouse where they've mocked up a mental hospital. Gort is strapped to a table where Dr. Drake administers electro-shock to disrupt Gort's memory and leave him confused.
Dan covers for the absence of the holder saying that the real Wilson doesn't use one. The U.S. undersecretary Jonathan Davis is arriving later and Dan is to meet with him.
A restrained Gort wakes up in the room and Barney takes him to see the doctor, Rollin. He claims that Gort is actually George Kroll, an accountant who thinks he's secret agent Gort. While Dan and Kiri meet with Davis, Rollin dismisses Gort's entire life as a figment of his imagination. Rollin reviews Gort's "imaginary" history and how he kidnapped an American envoy and took his place. The team is unaware that two small boys have slipped into the warehouse. Rollin wants Gort to explain the full plan to demonstrate his progress, but when he refuses they drug him (with a hallucinogenic) and take him back to his cell. The boys set off an electric eye-beam alarm and Willy chases after them while the team continues with their plan.
Willy corners the boys and convinces them that he's a homeless man looking for shelter so they won't tell the police. The rest of the team play sounds of people screaming into Gort's cell which combined with the hallucinogenic further disorients Gort.
Dan goes over the guest list and notices the Head of Security will be there. Piri notes that he will make the perfect witness for their plan. Dan manages to invite Cinnamon as part of his cover and as another witness. He calls Cinnamon and invites her to the reception, letting her know Piri's plan will occur at the reception that night. With time running out, Barney takes Gort to the electro-shock room and prepares to give him a jolt. Gort demands to speak to Rollin and eventually gives up the entire plan to show that he's cured. At the house, Piri gives Dan a gun and tells him to shoot first Davis and then Wilson.
The team figure Piri will bring Wilson to the reception and prepare to attend. Barney prepares a bulletproof book that Rollin places in his jacket pocket. He and Cinnamon go to the reception while Kiri has the unconscious Wilson brought into his private study. Willy warns Davis and Rollin gives Davis his jacket with the bulletproof book. He then tosses out a cigarette with a message to Willy, telling him to go to the study. Willy and Barney then slip into the house with the unconscious Gort. They replace Wilson with Gort while Piri orders Dan to kill Wilson. Rollin gives him the go-ahead once Willy signals everything's in place.
Dan declares the U.S. agreement is an insidious plan to take over the country then shoots Davis in the chest (and the bulletproof book). Dan runs into the study, fires a shot, puts the gun in Gort's hand, and goes out through the window. Kiri and the others come in and find the seemingly dead Gort-as-Wilson. Kiri explains "Wilson's" supposed motive for killing Davis, but the now undisguised Dan comes in and reveals who Gort really is. The authorities have Kiri taken away while Barney and Willy bring in Wilson.