Prisoner 9-1137 is discharged from prison with $2,000. A man waiting outside informs the killer that the target is camping and the trails are marked, but he has a couple of people with him. When the man asks why the killer wants to talk to the target first, the ex-convict ignores him and tosses him the $2,000.
MacGyver and Pete are mining for gold while Jack Dalton is busy taking pictures. MacGyver is skeptical they're not going to find anything but residue from an old mine but Jack insists they'll be rich. He insists it's fate that he won the claim to the gold mine in a poker game, and there must be gold. MacGyver finishes his makeshift sluice box and has Jack start pedaling on a bicycle to provide the power. When he starts bicycling too fast, Pete ends up getting soaked and all they end up is a fingertip's worth of gold.
The killer finds MacGyver's jeep, then dons a camo mask and takes out a handgun, and proceeds down the trail.
As Jack laments his fate, Pete and MacGyver remember the time when Jack bought a third-rate plane and MacGyver had to help him land by climbing down to the landing strut and then parachuting clear. Pete warns him there's nothing like a free ride but Jack doesn't believe it and goes back to work.
As the killer continues through the woods, the guys go back to work and Jack suggests they scout upstream for a motherlode. MacGyver warns that he won't go into another mine after the last time they blew up $5 million dollars. They point out Jack tends to drag them into trouble, like the time he involved MacGyver with a jewel heist and the police. Jack notes it's just a small detail and misremembers how Pete came to rescue them. Pete decides to take a break and go fishing. He's unaware that the killer has arrived and is drawing a bead on him. However, the killer decides to knock him out instead, then tie him up and fires off several shots. As it starts to rain, MacGyver and Jack hear the shot and go to investigate. They find Pete's tackle box, abandoned, then spot his hat and rod nearby. MacGyver finds two sets of tracks and follows them into the woods.
The killer takes Pete toward a nearby cliff and refuses to answer his questions. MacGyver finds Pete's Phoenix Foundation ID and figures Pete is trying to leave them a clue. He notes that Matt Weber tried to frame Pete during a missile test, causing an explosion in the process and forcing Pete to temporarily retire. However, they wonder why Weber wouldn't have killed Pete immediately. When they wonder if the killer is playing games, Jack suggests that Murdoc might be up to his old tricks, like the time he set Pete and MacGyver up in a cab, or when he came after MacGyver when he had gone into retreat at Pete's cabin.
The killer ties Pete down at the edge of a cliff and goes back along the trail. Jack and Pete spot Pete's wallet but approach it carefully, suspecting it's a trap like the explosive bed Murdoc once left for MacGyver. MacGyver uses Pete's fishing rod to pull it back and determine it's safe. The killer watches them from the woods as MacGyver sends Jack to go to the nearby grocery store to call for help. The killer removes her camo mask to reveal she's Deborah, who tried to kill MacGyver as part of her assignment. She briefly remembers her time together with MacGyver, then goes after Jack and captures him at the jeep. She forces him to drive to where she parked.
MacGyver continues along the trail and finds Pete's wristwatch hanging from a branch. Meanwhile, Deborah takes Jack to where she has Pete secured, and Pete asks why she's playing games. Deborah explains that she and MacGyver have unfinished business. Pete remembers how she tried to kill MacGyver in a boating accident and ended up blinding him instead. She explains that she's using them as live bait to lure MacGyver in.
MacGyver finds the jeep, along with Jack's hat and a note from Deborah telling him where they are. MacGyver realizes who he's dealing with and how she first seduced him and then tried to kill him after he was blinded in the explosion, but he managed to knock her out and turn her over to the authorities. MacGyver goes to the cliff and spots Pete and Jack, bound and gagged. He circles through the woods and Deborah comes out and tells him to come out or she'll kill them.
MacGyver emerges and Deborah explains that she spent two years in prison because she failed for the first time. She blames MacGyver because she let her feelings in the way, and that he won because she couldn't find anything in him to hate to give her an edge. As they talk, Jack manages to snag a rock with his foot. Deborah explains that she needed to look MacGyver in the eyes and see if she could kill him despite her feelings. She tells him goodbye, but Jack manages to hit her with the rock. MacGyver disarms her with the telescoping fishing rod and knocks the gun to the edge of the cliff. When she goes for it, Pete trips her and she falls over the edge. She manages to grab a root and hangs on, then braces herself on a ledge. She feigns losing her grip to get MacGyver to grab her arm and pull her up, then goes for a knife. She tries to stab him and grazes him, and the ledge gives way beneath her. She falls to her death as MacGyver looks on, helpless.
Later, the police take away Deborah's body and Jack wonders why she tried to kill him after he tried to save her. Pete remembers the story of the scorpion and the turtle, and how the scorpion killed itself because it was its nature, even though it killed itself in the process.