MacGyver returns home from a long, tiring mission only to discover Pete waiting for him with yet another assignment. When MacGyver refuses, Pete pushes the matter, angering his friend. MacGyver goes inside only to discover phone messages from Jack Dalton asking MacGyver to invest in a map, and Penny Parker wanting him to hear her perform her song at a Wild West show. MacGyver erases them and puts in a tape of Gunfight at the O.K. Corral, then dozes off in front of the TV.
MacGyver dreams that he's a Civil War veteran heading west to find peace and quiet in the town of Serenity. He travels with the driver, a Swiss immigrant named Emmenthaler. Emmenthaler drops him off on the town outskirts and MacGyver gives him his gun, saying he doesn't plan to shoot it ever again. In return Emmenthaler gives him a Swiss Army knife and drives away.
MacGyver stops at the Red Dog Saloon and orders a meal and a bottle of milk. The two local thugs, Wilt and Milt Bozer, start harassing him. The saloon girl, Penny Parker, tries to defend MacGyver. The resident gambler, Andrew Jackson Dalton, intervenes but the Bozers try to force MacGyver to drink alcohol with a spider in it. MacGyver borrows Dalton's cigar, throws it down Wilt's pants, and throws the drink in Milt's face. The marshal and bartender, Wyatt, finally intervenes and kicks the Bozers out.
Dalton offers his new friend the deed to the Big Springs Ranch and MacGyver, wanting to buy some land and settle down, soon agrees. They go out to see the ranch and Penny tags along. At the ranch, MacGyver and the others meet former owner Dave Nye's remaining two employees, Billy Colton and Lee Sing. When Lee Sing says the ranch is a dangerous place, Dalton quickly overrides his concerns. However, land baron Pete Thornton arrives with his men, including the Bozer brothers. Thornton insists that Nye agreed to sell the land to him but Dalton points out that he won it in a poker game and Nye never sold. Thornton, unimpressed, insists he needs the land so he has water for his ranch. Thornton tries to provoke the unarmed MacGyver, who finally punches him. When the Bozers go for their gun, Billy fires a warning shot and orders them to drop their guns and get off MacGyver's land. Thornton and the others agree but the land baron warns that he'll be back.
Back in Serenity, Thornton sends a telegraph to hire a professional gunfighter: Murdoc. The killer arrives in town by train, and the Bozers are unimpressed. Murdoc shoots a sign down on them and asks Thornton what he wants done. The land baron tells him to get MacGyver off the land but not to kill him.
MacGyver settles in at the ranch and soon realizes that Billy is a lot smarter than his fake accent indicates. Billy explains that he worked as a schoolteacher slave in Alabama, forged release papers, and moved west to create a new identity for himself. He continues acting ignorant because no matter what the law says about emancipation, some people are still prejudiced. MacGyver tells him that he has to have some faith and that anybody can reinvent themselves.
MacGyver rides into town and Dalton and Penny warn him about Murdoc. MacGyver decides to resolve things with Thornton peacefully and goes to see him. Meanwhile, Murdoc rides out to the ranch and orders Billy to tell him where MacGyver is. When Billy refuses, Murdoc casually guns him down. He tells Lee Sing to tell MacGyver that he was there and rides away. MacGyver arrives and can only cradle his dead friend in his arms.
Murdoc reports to Thornton at the barber shop where the latter is getting a shave. Thornton tells him he didn't want any killing and tells Murdoc to leave town. Murdoc refuses to have it said that he failed at a mission. He starts to draw on Thornton, who has a hidden gun ready. Murdoc leaves but says that it isn't the end of the matter. As the land baron leaves, the Bozers wonder why he's dropping the matter but Thornton insists that even though he was shamed, it isn't worth a man's life. He rides out to talk to MacGyver as the veteran buries Billy. Thornton apologizes and offers to pay any fair price, but MacGyver says he isn't interested in selling his land, but living on it. However, he offers to give Thornton free access to the water as long as he pays the drilling costs. Thornton is pleased to agree and insists on going with MacGyver as he rides into town to bring Murdoc to justice.
Meanwhile, Murdoc recruits the Bozer brothers, offering them revenge on MacGyver for his humiliating them earlier. They go to the saloon, capture Penny, and tell Dalton to tell MacGyver that they're waiting. Dalton rides out to warn them while the Bozers set up an ambush. Wilt fires early, warning the three men. MacGyver goes on ahead to get Murdoc and leaves the Bozers to Thornton and Dalton, who easily take care of them. MacGyver spots Murdoc on a balcony and scales the roof to come up behind him. However, he discovers that Murdoc has put a black coat and hat on Penny and tied her to the balcony. The killer comes up behind MacGyver and shoots him in the heart, sending him tumbling to the street below.
As Murdoc rides off, Thornton, Dalton, and Penny go to MacGyver's body. MacGyver coughs and sits up: the Swiss Army knife in his breast pocket deflected the bullet, leaving a noticeable dent. They watch Murdoc leave and Thornton promises that they'll get the killer one day.
MacGyver wakes up as Pete pours himself some water. MacGyver's friend apologizes, saying that he was pushing too hard to impress the board. MacGyver tries to explain what he was dreaming about. Pete points out there's an antique Swiss Army knife lying on the floor: a knife with a indentation left by a bullet.