MacGyver is being smuggled out of East Berlin in a coffin. His "pallbearers" drive him to a bridge at the border crossing and the guards have them set the coffin down in the middle of the bridge. Three "mourners" from the western side come over to collect it, but the head of security gets a call and sounds an alarm. The mourners toss the coffin over the side of the bridge into the water below. MacGyver triggers a remote and the sides of the coffin blow out, revealing a wood-paneled jet ski. He rides it away from the bridge as the guards try to shoot him.
Quayle, a foreign agent, addresses his three shadowy superiors and tells them that he plans to recover the microfilm that MacGyver has smuggled out of the country and is taking to American intelligence. His superiors warn him that this is his one and only chance to redeem himself.
MacGyver arrives at a helipad in Los Angeles and emerges onto the street below. Several foreign agents move toward him but an attractive blonde woman, Karen Blake, pulls up in a sports car and say she's his girlfriend. She warns him about the enemy agents and gets him into the car. As they drive away, she explains that her job is to deliver him to a special safehouse that Pete Thornton has set up. They arrive at the expensive manor, unaware that Quayle is in control of the house. He has the entire place wired and is controlling it from an underground center. He watches as MacGyver meets with Pete, and Pete admits they have a security leak. Pete's set up the entire thing on his own to keep the news from getting out.
Pete takes MacGyver and Karen into the trophy room and introduces them to Mrs. Chung. Pete tells them that Mrs. Chung will be decrypting the microfilm while they all wait. Mrs. Chung goes to the computer but it starts up on their own. Quayle greets them via the loudspeaker and triggers an explosive charge in the computer. He then seals all the doors and windows. Mrs. Chung tries to open the trophy room door and a poison needle extrudes from the knob. She collapses and Quayle boasts she's not the one he's after. MacGyver explains that Quayle is an agent who he defeated selling stolen computers, and Quayle warns that he's going to kill MacGyver and recover the microfilm. Pete tries to call out but the phone receiver disintegrates in his hand.
MacGyver, Karen, and Pete go to the main door and realize that Karen's car has disappeared. MacGyver tests the door and determines there are no traps attached to it. He slides a suit of armor outside, trigging the motion-sensitive machineguns. After gathering the pieces of armor, they go to the kitchen. MacGyver and Pete fake a conversation complimenting Quayle while MacGyver uses a metal bowl and a blender to build a jamming device. Once they jam the cameras, Pete says he has a radio phone in the trophy room. Pete makes the first attempt to escape, heading for the trophy room.
As Karen talks about her childhood and her lifelong dream to be a spy, Pete gets to the trophy room and finds the hidden radio phone. However, Quayle is monitoring it in and sends an electrical shock through it, knocking Pete unconscious.
Karen prepares to go out next to draw Quayle's fire. They kiss for luck and, after she leaves, MacGyver assembles batteries and hooks them up to a handheld mixer. He then tapes it to a cart, attaches the mixing head to the wheels using a rubber band, and wires together the armor headpiece on top.
Karen goes to a secret door and opens it. She comes in behind Quayle... who is waiting for her. She's worried that Quayle is dragging things out and jeopardizing their mission to recover the microfilm. Quayle tells her to worry about someone close to her, and orders her to find out what MacGyver is up to. He gives her a portable radio and lets her out.
Karen watches via a peephole as MacGyver finishes his work on the cart. She contacts Quayle and tells him MacGyver is going out the back door. MacGyver releases the cart and it moves along the hedges, drawing machinegun fire. MacGyver crawls on the ground behind it. He then shoves the cart in one direction and jumps over the hedges in the other. He gets clear of the grounds but Quayle calls to him on the loudspeaker, warning he'll kill Pete if MacGyver doesn't return.
While MacGyver returns to the house, Quayle tells Karen to get the microfilm. She and MacGyver meet in the trophy room and as Karen comes in, she says that Pete's been electrocuted. They make him comfortable find the unconscious Pete. MacGyver figures if they can cut off the power supply to the house, they can dispose of Quayle. He then takes the radio away from Karen and demands to know what she's up to. She confesses she's a double-agent and wonders how he knew, and MacGyver explains she knew Pete was electrocuted before she could get close enough to tell, and the men at the helipad didn't make a serious attempt on his life. Karen explains that Quayle has her brother, a fellow spy, and he's blackmailing her into cooperating. MacGyver promises to rescue her brother in return for her help and she agrees.
MacGyver and Karen head for the secret passageway but Quayle triggers internal motion-sensitive guns in the hallway. MacGyver uses vinegar and baking soda to create a smoke screen, and then Kate opens the hidden panel. Quayle is sealed inside his bunker so MacGyver heads for the power room. They scatter piping across the hallway outside and then MacGyver requires the panel to expose the wiring. He has Karen pile up debris so there's only one way to enter the room, past the wiring, and then he puts a mirror in a piece of duct piping to use as a periscope. Finally, he rigs a pressure valve on a water heater to fire a burst of water.
MacGyver cuts the power and Quayle comes to investigate. When they hear him outside moving the piping, they kiss for luck and get into position. Quayle comes in but the periscope is at the wrong angle. Karen reaches up to adjust it and Quayle spots her. She quickly comes out of hiding and says she was pretending to help MacGyver to set him up for Quayle. Quayle lets her get close enough so that she can turn against him and shove him into position next to the wiring. MacGyver releases a burst of water that sprays Quayle and the wiring, stunning him. MacGyver knocks away his gun and punches him unconscious.
Later, a recovered Pete calls his superiors to report what happened, while Mrs. Chung wakes up and MacGyver tells her that everything's taken care of.