At an airport, assassin Nicholas Varsi arrives and opens a locker only to find it empty. A man agent approaches him and demands his passport for identification. He provides him with the papers for a new identity and then Ben Nelson, an agent for the Federal Intelligence Service, arrests them both. Varsi claims that he is defecting.
Jim picks up his briefing from a repairman on a rooftop, and is informed that Varsi is defecting but refuses to reveal his assassination mission unless he is granted asylum. The FIS is under suspicion of being infiltrated by a deep agent so the IMF must kidnap Varsi out from under their noses.
The team goes over the Bancroft apartments where the FIS is keeping Varsi. They have a mask of Willy made and Barney has a voice-sensitive truth device but IMF agent Andrea notes that a trained agent might be able to fool it.
Varsi is being interrogated by Nelson, and lays out his demands for asylum. Nelson acts interested but after he leaves, notes that they're going to have to wait a while to put pressure on him. Barney walks by and tosses an explosive in the window, then policemen Jim and Willy arrive to check it out. They secretly plant four miniature timed explosive charges then drug Varsi. The charges go off and Jim and Willy put the Willy mask on Varsi. Willy slips out the window while Jim takes the disguised Varsi out claiming he was shot by an intruder. Barney and Andrea then take him away in an ambulance. Nelson notices Varsi is missing but is fooled by the fake wound they've put on Varsi. After they're gone, Nelson quickly figures out what happened… just as they escape. He sends one of his men in pursuit and Jim drops off Willy, who releases some barrels behind the ambulance.
Varsi wakes up in an empty winery and is taken to Jim, who is posing as the head of intelligence in the U.S. for Varsi's superiors. When he demands to know why Varsi was defecting, Varsi claims he lied so that he could carry out his mission, and his superior Colonel Kremmer knows about him. Varsi refuses to compromise security by providing assurances and Jim threatens to keep him there. As Varsi is taken out, he gets a glimpse of a sobbing Andrea.
Nelson expands his search of the city while Andrea is put into a room with Varsi. She claims she's with the FIS and was taken along with him. He spars with her over whether he defects and whether he trusts her, then kisses her.
While Nelson closes in, the team meets and Andrea believes Varsi is telling the truth, but the lie detector reading is indeterminate. They take Andrea back in and Jim gives Varsi a gun and tells him to kill her to prove his loyalty. He does so.. and the gun is unloaded. Jim releases Varsi to conduct his assignment. and he asks for Andrea to use as a hostage.
Nelson has narrowed down the search, while Jim figures Varsi will turn Andrea over to the FIS if he's sincere about defecting. They track the car as he has Andrea drive to an electronics store. He puts her in the trunk then goes inside, then comes out with an electronic device for locating bugs. He finds the tracking device the IMF is using, planted in his collar. He ditches it and leaves, and they stop at a gas station to refuel. Andrea activates a new signaling device and the team moves to intercept. However, the attendant notices the electronics detector and turns it on, revealing Andrea has a bug on her as well.
Varsi goes to a hotel room after tying up Varsi, and reveals someone has left a gun for him. He's waiting to meet with Kremmer while, Jim, Barney, and Willy spread out in hope they'll get Andrea's signal when she gets a chance to send one. As Varsi prepares for the kill, Andrea manages to dial Jim and tap out the room number due to her gag. She manages to get back in position just in time, although Varsi doesn't notice the phone slightly off the hook. Kremmer then arrives at Varsi's room… except it's Nelson.
Varsi reveals that he plans to give the Americans Nelson, but Nelson anticipated it in and put a defective firing pin in the gun. Nelson wounds Varsi then brings out Andrea and forces her to tie up Varsi. Nelson prepares to go ahead with the assassination at the government building across the street, and leave Varsi as the fall guy. Jim spots the gun barrel and climbs up while Varsi and Andrea manage to knock over a table, distracting Nelson so Jim can burst in and disarm Nelson.
Varsi is taken out in an ambulance, and Andrea leaves him with his questions about who she really is unanswered.