MacGyver takes his truck to get washed and chats with the worker, Chauncey. Chauncey offers to take it off his hands but MacGyver insists that it's a classic. As they're talking, a woman walks by and compliments MacGyver on the car before leaving.
Sofia Parker is walking her dog along the river. As she stops to talk to an old woman, her dog Frog runs off after another dog into an amusement park. Sofia goes after him. Meanwhile, three men are meeting and reading a letter saying that the piece of the map that each one has will lead them to the Black Corsage, hidden in the park. Deegan asks to see the pieces but Reynolds insists that Deegan show them his first. Deegan and the third man, March, show Reynolds their pieces. Once Reynolds reveals his piece, Deegan draws a gun. Reynolds makes a run for it but Deegan shoots him. Wounded, Reynolds stumbles into a carousel and manages to turn it on. Meanwhile, Sofia slips through the gate to find Frog. The dog hears the carousel and starts barking. Sofia ties the dog and goes to investigate. Reynolds stumbles into her and slips his piece of the map into her pocket, then runs off. Sofia runs away, leaving Frog, Reynolds collapses and Deegan and March search him but don't find the map piece. They realize that Sofia has the piece and go after her.
Sofia goes to a phone booth and places a double red call to Pete Thornton at the Phoenix Foundation, using the codename Dolphin. However, Deegan shoots at her before she can complete the call and Sofia is forced to run, dropping her purse. She gets away and March chases after her. Deegan picks up the phone and hears Pete at the other end. Deegan pretends to be a homicide cop, calls the operator, and traces the call back to the Foundation. Meanwhile, Frog pulls free from his leash and runs away.
Later, the police examine the crime scene and MacGyver arrives to get an update from Pete. Pete explains that Sofia, a Bulgarian defector who is with the Foundation relocation program, called from the park. They can't tell the police anything without compromising their program.
Outside, a man examines Frog's abandoned leash and finds his dog tags.
Deegan and March go to Sofia's address. Going through Sofia's purse, Deegan finds a photo of her with MacGyver at the houseboat and a Bulgarian passport. There's also a security ID for the Foundation identifying her as a researcher. March doesn't find anything inside
Sofia goes to the Phoenix Foundation but spots Deegan outside, talking to a security guard. Panicked, she runs away.
MacGyver goes to Sofia's house and finds Frog waiting. He goes inside with the dog and discovers someone has ransacked the place. He spots movement from the closet but when he investigates, a man quickly handcuffs and subdues him, calling him "Deegan." However, the man identifies himself as Frank Colton, a bounty hunter and Jesse Colton's brother. He takes MacGyver out to his car and frees him, and admits he took over Jesse's files while Jesse is in Hawaii. Neither one wants to tell the other what they know but Frank warns that Deegan is a heavy hitter and MacGyver will need help. When MacGyver starts to drive away, Frank mentions the map, catching his attention. MacGyver has no choice but to take him along.
At a switching station, March is tapping Pete's phone line. He calls Deegan, who has located MacGyver's houseboat from the photo. March realizes that there's top security on the phone line and warns that there's something going on.
MacGyver and Frank talk to the security guard, who explains that Sofia hasn't been there but Deegan and March were asking after her. MacGyver calls Pete and says he's heading for the research lab. Pete has checked and is sure Sofia's disappearance has nothing to do with the Bulgarians. MacGyver insists that it's time to exchange notes and explains that Sofia was the daughter of an author in Bulgaria who wrote a pro-democracy book. After he died, MacGyver helped her escape to the U.S. where she was given a new identity. Frank shows him a photo of an expensive necklace, the Black Corsage, set with a large black pearl. Deegan and four other men penetrated a computer system to steal the Black Corsage. Simms was caught but the Corsage was never found. He was killed in prison but sent pieces of the map to his three accomplices. Frank tracked them to the amusement park, found the dead man, and figures he gave his piece to Sofia. He insists he's doing it out of the goodness of his heart, but MacGyver figures the insurance company has put up a reward and Frank is after it.
Sofia goes to the train station and calls Pete's number. As she goes through her pockets, she finds the piece of Reynolds' map. Sofia then places the call and tells Pete where she is. Pete tells her to go to a nearby diner and meet with MacGyver, unaware that March and Deegan are listening in. They realize she has the map piece and head for the diner. As Sofia leaves the train station, she spots promotional cardboard standup of the Statue of Liberty and hides the map piece in the torch.
MacGyver and Frank go to the research lab but there's no sign of Sofia. Pete calls MacGyver and tells him to meet Sofia at the diner. He's surprised to hear that MacGyver is working with a Colton again.
At the diner, Sofia knocks a spoon on the floor. When she bends over to pick it up, Deegan come in but fails to see her. She spots him and hides as he sits in the diner next to hers. Sofia also spots March outside and slips out the back. As she goes, she snags her dress on the door jam. As Sofia runs off, MacGyver and Frank arrive out front. MacGyver tells Frank to stay with the truck and Frog. MacGyver goes inside, walking past Deegan who he doesn’t recognize. Deegan recognizes MacGyver from Sofia's photo. The waitress recognizes Sofia from MacGyver's description and tells him that she went out the back. MacGyver goes out back and meets Frank and Frog, and Frog finds the piece of dress. The dog starts following Sofia's trail and the two men chase after him, while March and Deegan follow them.
Sofia goes to a nearby fish processing plant and hides inside. Frog follows the trail and leads the men inside the empty plant. The dog finds his mistress and Colton draws his gun, cornering her. She grabs a knife but MacGyver manages to calm her down and assures her that Frank is a friend. March and Deegan arrive and get the drop on them. Frog attacks March, who prepares the shoot the dog. Frank tries to help Frog and Deegan shoots him in the shoulder. Frog runs off and Deegan demands the map. When Sofia refuses to tell him, Deegan ties MacGyver and Frank up and places them on a conveyer belt. She finally gives in once Deegan gives his word he won't harm Frank and MacGyver. Once March takes her to the car, Deegan turns the conveyer belt on and the two men move toward a grinding machine.
MacGyver spots Frog and calls him over. He tries to get the dog to bring a hose over. Frog ignores him and walks over to a table with a knife on it. Frank tries to call Frog over but the dog ignores him as well. With only a few seconds left, Frog hits a lever that reroutes the conveyer belt, dumping the men in a bin full of dead fish. Frank figures the men will return to the amusement park to recover the Corsage.
At the train station, Deegan and March recover the last piece of the map and realize the Corsage is hidden in the carousel. When Sofia tries to leave to go free MacGyver and Frank, Deegan stops her and takes her with them to the park.
MacGyver, Frank, and Frog get to the amusement park ahead of the two criminals. Deegan and March come in and realize that Simms hid the Corsage in plain sight on a dummy at the center of the carousel. As they shoot open the case, MacGyver and Frank slip under the carousel to the inside control center. March recovers the Corsage and Deegan prepares to shoot him. MacGyver turns on the carousel and March runs for it. Frank punches him unconscious while Deegan shoots at the bounty hunter. MacGyver grabs the Corsage and runs, distracting Deegan when he tries to shoot Sofia.
MacGyver runs into a video game arcade building and goes through the booth. He finds one with an electronic gun and rewires the cable to the Corsage. He then runs a cable to the support holding up the awning and ties it to one of the moving targets. Finally he tosses his shirt outside the door and sets off the fire alarm. Deegan comes to investigate, sees the shirt, and enters the arcade. MacGyver turns on the power, bringing the awning down on Deegan. When he drops the gun, MacGyver kicks it way and Frank captures Deegan.
Later, Pete and MacGyver are relocating Sofia again. March has testified against Deegan and Frank has collected the reward. Sofia comes out with Frog and Pete explains she'll have to leave the dog behind so she doesn't compromise her new identity. She gives the dog to Pete and leaves. When MacGyver suggests it'll have to go to the pound, Frank figures they're trying to get him to take it. However, he takes the dog anyway and it hauls him off to his car.