Jesse Colton and his dog, Frog, are investigating a warehouse where a counterfeiter, Egan, has captured Frank Colton and MacGyver. As Jesse approaches the warehouse, Egan ambushes him and shoots him twice in the chest. After Egan leaves to pick up his partner, Jesse staggers up and pries the bullets out of his bulletproof vest, and then runs after Egan as the counterfeiter pulls out. Jesse leaps into the back of the man's truck, smashes in the back window, and shoots out the dashboard, causing the truck to crash. The bounty hunter interrogates the two men and demands to know where Frank and MacGyver are.
Frog wanders off into the warehouse and finds Frank and MacGyver tied up. Egan has left a bomb for them and time is running out. MacGyver spots a bottle of sulfuric acid and notices that Frog is in the window. They both try to get Frog to come in and bring the bottle over. The dog proves initially uncooperative, but finally brings it over. MacGyver uses his feet to nudge a board onto a roller and then gets the dog to put the bottle on the board. When he kicks his end of the board, the bottle flies up into the air and MacGyver manages to catch it. He burns the through the acid and the two men run out of the warehouse just in time as the bomb detonates.
Later, Jesse and Frank go to their mama's house. She tells them MacGyver is avoiding news reporters asking about the counterfeiting case by taking a vacation in the mountains. Meanwhile, Billy is there and working on his college application. Chief Inspector Johnny Denmark shows up to hire Jesse and Frank. He wants them to find a girl named Medusa, the girlfriend of a Chinese crime lord. Chi, his rival, killed the crime lord but Medusa saw the murder and escaped. Since Chi has the Chinatown police in his back pocket, Denmark needs the Coltons to find the girl.
Frank and Jesse go to the restaurant where the crime lord was killed. The owner claims she doesn't remember seeing Medusa. As they talk, two local cops, Danko and Quilla, arrive and pick a fight. They toss Jesse out and even Frank isn't able to calm them down. As they leave, the owner gives Frank a piece of paper with Medusa's real name: Patricia Fielding.
The brothers have Mama run a check on the name. Patricia is the daughter of G. Irwin Fielding, a former savings & loans officer who was charged with fraud when he ripped off his customers. Fielding's wife is Loretta Wu, a former fashion model. Mama Colton comes up with the private yacht club where the Fieldings are having lunch. Frank and Jesse leave for the club and Billy asks Mama Colton if he can skip going to college and start in the family business as a bounty hunter. Mama insists that he get a college education. However, once she leaves, Billy writes down the yacht club address and leaves to go help his brothers.
Loretta arrives at the club and finds her daughter outside. As they talk, Jesse and Frank arrive and see them go inside. However, two of Chi's men are watching them and call to tell their boss that the Coltons have found Medusa. Chi tells his men to dispose of Medusa and the Coltons. Meanwhile, Billy arrives with Frog and sees the two mobsters getting guns from their car. Billy gets to Jesse's truck, grabs his shotgun, and sneaks inside the club.
In the club, Patricia is arguing with her father and trying to get her to understand she needs her help. He's unsympathetic because she hangs out with criminal types and is willing to let her suffer the consequences. Jesse and Frank arrive and offer her their protection. Outside, Frog attacks one of the killers as he opens fire and the shot goes wild. Frank takes on the first killer as the second one goes inside and opens fire. Billy arrives and tosses Jesse his shotgun. Jesse brings down a chandelier on the second killer while a panicked Patricia escapes in a nearby boat.
The brothers are out of clues but Loretta calls to tell them they can find Patricia at a hair salon owned by one of her friends. As they arrive at the salon, Jesse notices that Danko and Quilla are following them. They get Patricia out of the salon and the cops follow them. Frank calls home and talks to Denmark, who is waiting with Mama to learn when they've found Patricia. He tells Frank to take Patricia to a boatyard and turn Patricia over to his assistant, Charles. However, once he hangs up, Denmark makes a second call... to Chi. He tells the crime lord when he can find Patricia. He leave but Billy notices what number he called. He has Mama track it on Frank's advice.
As they wait at the boatyard, Jesse figures that Danko and Quilla are so incompetent that they must be legitimate cops. However, that leaves the question of who Chi does have working for him. They realize that Denmark is working for the crime lord, but Chi and his men arrive and take them captive just as the Coltons figure out they've been betrayed.
Mama Colton has one of her sources at the phone company confirm that Denmark called Chi's number. Billy insists on going after his brothers and saving them. After he leaves, Danko and Quilla arrive and tell Mama that they want Frank and Jesse. She recognizes them as the men who attacked Jesse at the restaurant and tells them it's time for a talk.
Chi's men hang Jesse and Frank up from the rafters of a warehouse. They then bring in illegal Chinese workers that Chi is smuggling into the U.S. to work for him preparing drug shipments. They show the Coltons as an example of what happens to those who cross Chi and then shoot them dead. However, once Chi's men herd the workers away, Frank and Jesse stop playing dead: they're both okay thanks to their bulletproof vests. However, a guard is posted nearby and they can't get free without giving themselves away.
Billy arrives with Frog and sneaks onto the ground. Frank starts sneezing and he realizes that Frog is nearby. They quietly call Frog over to distract the guard. Once he's checking on Frog, Jesse and Frank free themselves and drop on the guard, knocking him out.
Billy sneaks into the main warehouse and tries to pass himself off as one of the workers putting drugs in Chi's stuffed lizards. However, the guards realize he's an intruder and take him to see Chi, who is meeting with Denmark. Frank and Jesse realize that Billy has been captured and climb up into the rafters and sneak over toward Chi's office.
When he sees Billy, Denmark figures that the Coltons know that he's crooked. Chi tells his men to pay off Denmark and then dispose of Mama Colton, and demands that Denmark kill Billy personally so he'll be tied to Chi as an accomplice to murder. Denmark balks at committing murder. Outside, Mama arrives with the police and they burst into the warehouse. The workers panic and Chi realizes something is up. However, Frank and Jesse drop through the ceiling and tackle Chi and Denmark. They push them through a window and into a dumpster below. Frank lands on Chi, knocking him out, and Jesse knocks Denmark out. Billy captures Chi's assistant before he can shoot his older brothers.
Afterward, Mama Colton brings over Danko and Quilla and explains that she convinced them that they were all working to bring down Chi. When they realize that Billy is okay and helped save the day, Frank and Jesse suggests that Billy might work for them part time. Mama reluctantly agrees and admits that she's letting go... a little.
Later, MacGyver returns from his mountain retreat and discovers that Jesse is putting up a sign announcing that the Coltons are now a detective agency. They need the money because Denmark never paid them.