MacGyver arrives in the forests of East Germany and meets his contact, Fritz. Fritz, a hunter, gives him a microfilm stored inside of a shotgun shell. Soviet soldiers arrive and MacGyver tries to bluff his way out, then throws a dead bird from Fritz's collection to the dogs, distracting them long enough for the two men to run in opposite directions. MacGyver gets to the road but is forced to run into the woods again when a police car and a motorcycle officer close in. The car brakes to a stop and the motorcycle skids out of control. The car's driver is Craig Bannister, a fellow agent. MacGyver gets in and a soldier opens fire, severing a brake line.
Bannister drives downhill for the border but soon realizes the brakes are out. As they start to accelerate and the soldiers close in, MacGyver has Bannister pop the hood and then he climbs out to the front. As he hangs on and reroutes the power fluid lines into the brake cylinder, they run through the border checkpoint and the Soviet troops are forced to give up the pursuit. MacGyver succeeds and Bannister gets the car back under control. MacGyver gets back in and asks about Bannister's wife as they go on their way.
Back in the states, MacGyver arrives at headquarters and stops to talk to the security guard, Fritz, and pass on some letters from his family in East Germany. He comes into Bannister's office and finds him in an embrace with his new wife, Ingrid. MacGyver goes to see the new director and get Bannister some time off. It turns out that Pete Thornton is the new executive director. Pete tells him that they've lost four top agents in the last seven weeks and it's clear they have a mole. MacGyver instantly refuses to help, explaining he's preparing to move. MacGyver walks out but Pete goes to his house to try to convince him to take on the assignment. He hopes to set a trap, using a GRU Russian defector who can identify the key Soviet agents on sight. Pete admits that MacGyver is the only one he can trust. They're interrupted when the defector, Viktoria Tomanova, arrives. MacGyver objects to her being used as bait but Viktoria insists on helping. MacGyver still refuses and Pete invites him to a science symposium as a show of support. MacGyver agrees to help out.
Bannister and Ingrid attend the symposium and spot MacGyver in a tuxedo as he comes in. Pete and Viktoria arrive and Pete compliments her on her appearance, then thanks MacGyver for coming. They look at an ultrasonic beam display and Viktoria gently chides MacGyver. Then she spots the Russian head of the GRU, Anton Lem. MacGyver tries to escort her out but Viktoria insists on staying because Lem doesn't know her. Reverend Mather begins a speech, unaware that Lem has activated a small handheld transmitter. Lem triggers the device a second time and Mather clutches at his head, then reaches beneath the podium. He pulls out a gun and fires at Viktoria. MacGyver grabs the ultrasonic beam and aims it at Mather, shattering his glasses and causing him to collapse in pain. MacGyver and Bannister inspect Mather, who is rambling incoherently about someone telling him to use the gun. Before he can speak further, Lem triggers the device again and Mather clutches at his chest. They're unable to revive him before he dies of what appears to be a heart attack.
At the morgue, Ed the pathologist performs an autopsy on Mather, who discovers a mass of fibrous tissue in the heart. Ed agrees to give MacGyver a sample. Outside, MacGyver talks with Pete and Bannister and insists that it's too much to be a coincidence. He figures that whomever set up Mather is working with the mole inside of the agency.
Viktoria comes to visit MacGyver and apologize for her earlier rudeness. They flirt briefly and Viktoria notices that MacGyver is working with the sample from Mather's heart. He demonstrates that when the chemicals are exposed to a magnetic field, they turn into nylon and create a blockage. Viktoria figures Lem is responsible but warns that he's working with others.
At home, Bannister explains to Ingrid that MacGyver thinks Mather's heart attack was induced. She starts to give him a massage and then activates a hypnosis device. She then has him tell her about MacGyver's suspicions. Ingrid tells Bannister that Viktoria and MacGyver are the killers and he has to kill them. The hypnotized Bannister agrees. Lem calls and tells her that MacGyver has left for the science exhibition hall and taken Viktoria with him. Ingrid assures Lem that Bannister is ready and says she'll send him to the exhibition hall.
MacGyver plays back the security tape to see if she recognizes anyone else. They hear feedback when Lem activates his device and Viktoria thinks she recognizes the sound. They play it back but she still can't place it. MacGyver creates a crude hypnotic device to trigger Viktoria's memories. Before he begins, she asks him to kiss her. He gives her a perfunctory kiss and she demands a serious display. MacGyver obliges and she says that now she trusts him. Meanwhile, Ingrid drives Bannister to the exhibit hall where Lem has knocked out the security guard. She gives Bannister his final instructions and sends him inside. Lem warns Ingrid that it's a risk but she knows that Viktoria saw her and could recognize her at any moment.
MacGyver starts running word associations to spur her memories while he plays the tape. When Ingrid appears on the tape, Viktoria says her name is wrong and identifies her as a GRU intelligent operative. Ingrid comes in with Bannister and Lem and informs MacGyver that Bannister is the mole, but they're going to frame MacGyver. She figures that Pete may resign and Bannister will take his place. Bannister aims and MacGyver shoves a TV stand at him. Viktoria tackles Ingrid and MacGyver knocks out Lem, but Bannister recovers and prepares to shoot his friend. Viktoria prepares to shoot Bannister but MacGyver tells her to stop, then tries to get through to Bannister. MacGyver reminds them of all the missions they completed and the times they saved each other. Bannister snaps out of it but Ingrid activates the magnetic device, setting off a heart attack.
Viktoria knocks out Ingrid while MacGyver grabs a pair of candlesticks and connects them to microphone cables. He uses rubber matting to hold them then feed an electrical current through Bannister to disrupt the magnetic field and break the nylon clotting. Bannister recovers and Viktoria congratulates MacGyver.