MacGyver is checking out hot springs in Elm Creek, MN, as part of a geothermal project for the Phoenix Foundation. As he's driving back to his motel for the night, his car dies as he drives by a field. Getting out, he sees a glowing saucer-like object in the sky above. A man dressed in black is sitting nearby and casually comments to MacGyver that it's impressive. MacGyver spots a man in a silver suit beneath the saucer and walks up to it, but the figure knocks him unconscious.
MacGyver wakes up later and discovers that the saucer, the silver-suited figure, and the man in black have all disappeared. As he walks back to his car past the nearby high-power lines, he spots an abandoned house nearby. He goes there to call for help and a young boy, Tommy Wiley, runs away. MacGyver manages to catch up to him and convinces him he's not an alien. Tommy explains that the people who owned the farmhouse moved out several months ago under mysterious circumstances. MacGyver asks Tommy if he can use his father's phone and Tommy warns him that his father John doesn't like strangers. MacGyver insists and they go to the Wiley farmhouse. John is preparing supper for his sick wife and says he didn't see any lights. He lets MacGyver use his phone and goes to see his wife, Sarah. Tommy starts to warn MacGyver about something but his mother calls him upstairs before he can say anything useful.
The next morning, MacGyver gets back to his motel and finds the man in black outside. The man introduces himself as Phil Sternwise. Phil acts mysterious, claiming he didn't see anyone attack MacGyver, and notes that there have been a lot of UFO sightings. MacGyver dismisses them as natural phenomena and Phil wishes him well in his hunt for natural phenomena.
MacGyver goes to get his car from the mechanic, Parnell, who says that the electrical gear burned out. MacGyver points out that he just installed it a month ago but Parnell notes that there have been UFO sightings in the area and they tend to burn out electrical equipment. MacGyver goes back to the field and discovers a large circle of scorched earth. Using a Geiger counter, he determines that the area is radioactive. John shows up and explains he's the caretaker while the local owners are gone, and he wants MacGyver off the land. The Elm Creek sheriff arrives and identifies MacGyver, and suggests the scorched earth is kids playing a prank. He suggests that John back off and the man angrily stalks off. The sheriff then suggests to MacGyver that he spend his time working on the hot springs project rather than chasing aliens.
MacGyver goes back to his car and finds Tommy hiding in the back. Tommy wants to run away because aliens came from the spaceship and want to take his family to another planet. He explains that his mother is dying of cancer and the aliens say they can cure her on their home planet. MacGyver correctly guesses that the aliens want all of the Wileys' money and Tommy says that they're coming back that night. He tells MacGyver that he followed the aliens to the nearby campground where they're staying in a trailer.
MacGyver goes to the campground and finds the trailer, which has Illinois license plates. A man, Ray Rigel, emerges and asks MacGyver if he wants peace and love. However, his wife Dawn comes out and insists that MacGyver isn't a believer. They tell MacGyver to leave and go back in their trailer.
Later, the sheriff visits MacGyver at the small shed he's using for his research. MacGyver is analyzing dirt from the UFO landing site and determines that someone used napalm on it. He tries to explain that the Rigels are conning the Wileys out of their money but the sheriff doesn't believe him. He agrees to check the license plate number but tells MacGyver to stay away from John and his family.
That night, the Rigels visit John and tell him that their planet is a paradise where Sarah will be cured. However, they warn that MacGyver is interfering in their great plan and they need John to "neutralize" him.
The next day, MacGyver sneaks into the Rigels' trailer and finds a jar containing radioactive black rocks. He collects some and prepares to leave, but the Rigels pull up outside. As they start to come in, sure to discover him, Phil suddenly appears out of nowhere and offers to sell them a vacuum cleaner. As he talks, MacGyver manages to sneak out without being noticed. The Rigels go inside and MacGyver turns to ask Phil why he's there, only to discover the salesman has disappeared.
Back at his makeshift lab, MacGyver is working with electrical wires when the sheriff arrives. MacGyver demonstrates that someone could create an electro-plasma discharge by sparking off ammonia fumes around a high-power line. He explains the whole scheme to the sheriff: the Rigels faked the UFO saucer, salted the ground with the black radioactive rocks, and used a flamethrower to create the scorched landing site. The sheriff still doesn't believe it and further, informs MacGyver that he's under arrest. John Wiley has filed a trespassing charge with the county attorney, claiming MacGyver was back on his land the previous night. He has no choice but to arrest MacGyver.
The Rigels go back to the Wiley farm to thank them for his help. They insist that John must turn over his life savings to prove that he has divested himself of material goods and is worthy to go with them. John and Sarah promise to have the money that night, unaware that Tommy is listening in.
MacGyver doesn't have the money to bail himself out, but an unexpected savior volunteers the money: Phil. Once he's released, MacGyver asks the salesman for answers but Phil claims that he's just a concerned bystander protecting his customers: the Wileys once bought a vacuum cleaner from him. He insists that he just keeps turning up in the right place at the right time because he's a good salesman.
Tommy rides his bicycle to the campground and slices one of their tires. However, Ray catches him and locks him in the trailer.
That night, MacGyver takes his electrical demonstration to the Wiley farm and tries to get John to look at it. The farmer, having second doubts, agrees to take a look but Sarah comes in and asks where Tommy is. She thinks that MacGyver has the boy and is holding him so they won't go with their benefactors. She complains about how God must intend for them to go to the Rigels' planet so she can be cured and convinces her husband to force MacGyver out. Outside, MacGyver spots high-power lines passing over the cow pen and drives around the farm to get to them. He starts scavenging barbed wire to perform his demonstration on a larger scale, and Phil mysteriously appears behind him to help.
The Rigels arrive with their trailer and tell John and Sarah that they locked up Tommy and he's having trouble accepting the truth. They ask for the money but John, realizing something is up, refuses to pay until they've been transported to the home world. When Dawn insists that he pay first, John figures they're conmen. However, the Rigels draw guns and demand the money.
As the Rigels escort the Wileys out to the yard, MacGyver rubs the barbed wire on a salt lick to improve its conductivity. The Rigels get Tommy and lock the entire family in the barn, and then set it on fire with the flamethrower they used to fake the landing site. MacGyver and Phil throw the barbed wire onto the high-power lines, setting off a spark that interacts with the ammonia fumes from the cow manure. MacGyver and Phil split up and the Rigels, distracted by the UFO, split up to chase after them. Phil knocks out Dawn while Ray corners MacGyver and prepares to set him on fire with the flamethrower. Phil comes up behind him, concentrates, and the flamethrower sputters out for no apparent reason. MacGyver knocks him out and discovers that Phil has vanished again. He goes to get the Wileys, but someone has already put out the fire and released them.
Later, the sheriff arrests the Rigels and finds enough evidence in their trailer to put them away for a long time. MacGyver assures Sarah that doctors are finding new treatments for cancer all the time. The sheriff hasn't had any luck finding Phil, who checked out of his motel room earlier that day. Tommy sees something outside and they all go out to see a larger saucer-like object in the sky. MacGyver is forced to admit that the object is moving and there are no high-power lines nearby, and it might be something he can't explain.