MacGyver and his neighbor Wilt Bozer are out biking to get Wilt some much-needed exercise. Wilt finally gives up, and MacGyver stops for a Sunday paper. A car pulls out of an alleyway, grazing MacGyver and knocking him over. The driver gets out and introduces herself as Lulu. She talks about her boss and friend Izzy, who wouldn't he happy if the car was damaged. She finally gets around to MacGyver, apologizing profusely. She offers him a lift because of the damaged bicycle, and MacGyver reluctantly accepts. As she drives like a maniac, Lulu explains that she borrowed the car for a party that night but can't find the invitation among the garbage in the bottom of the car. She plays a tape of Izzy's violin music and MacGyver realizes that he's a famous violinist.
Lulu decides to stop off at a pawnshop first to pick up something for Izzy that he left in storage. She finds the claim check but discovers the pawnshop is closed. Lulu drives to Izzy's manor to tell him that she couldn't get his package. She leaves MacGyver at the front gate and gives him a kiss, then goes inside. MacGyver discovers the party invitation in his newspaper and goes back to give it to her.
Inside the house, a thug named Ginko is trying to get Izzy to tell him where a package is by smashing his rare violins. When Lulu hears the commotion and comes in, Ginko's boss Tubbs comes in and asks her where the Amadeus is. Lulu doesn't know what he's talking about. When MacGyver hears them, he comes in and Ginko knocks him briefly unconscious. Lulu says she has the Amadeus and that MacGyver is her husband, so she'll give them the Amadeus. She insists on meeting them in a public place and spots the invitation MacGyver's holding, and tells them to meet her there. They leave with Izzy as a hostage.
Once the crooks are gone, Lulu reminds MacGyver that they'll be expecting him at the exchange that night. MacGyver reluctantly goes along with Lulu as she returns to the pawnshop. As he goes to call the owner's emergency number, Lulu breaks in and grabs Izzy's item: a bag of golf clubs. She says that the owner is Izzy's cousin and is fishing in Canada, and he'll understand why she had to break in. They drive away before the police arrive and pull off in an alleyway. Inside the bag they find an antique violin and a certificate of origin confirming it is a Stradivarius that was owned by Amadeus Mozart. Lulu starts playing it and draws the attention of everyone on the street, who applaud when she's done.
That night, Lulu gets costumes for the party, which has a Roarin' 20s theme. When MacGyver goes to get some apple cider, Lulu switches the violin for a band member's. When MacGyver returns, they dance and he promises to get Izzy back. Tubbs and Ginko come in, wearing 20s police costumes, and pretend to arrest the couple. They put real handcuffs on them and Tubbs discovers that Lulu doesn't have the Amadeus with her. They start to take them out of the room to interrogate them further, but MacGyver knocks Ginko over and makes a break for it. They take refuge in a boiler room and temporarily lock the door out is a narrow window. MacGyver cranks the window open to make it appear they escaped and then hides in a vent with Lulu. Tubbs and Ginko come in and Lulu gives out a muffled scream when a rat runs by. Ginko goes to investigate but MacGyver puts the rat outside and Ginko assumes it made the noise.
After the crooks leave, MacGyver and Lulu climb out to a nearby shopping mall. Lulu explains that she switched violins and they go to find a bathroom. As they go up the escalator, Lulu starts discussing MacGyver's lack of a love life and he admits he's only been in love once. When a security guard spots them, MacGyver shows him his ID and convinces him that they're with the party. Lulu manages to steal the guard's keys and gets them free once he's gone. MacGyver tries to piece together the whole thing and figures that whoever shipped the violin knew Izzy had it. Lulu confirms that Izzy uses the same air freight company every time and they go to the airport. The customs inspector tells them that Ginko filed a damage report and that Tubbs came by a half-hour ago to tell him not to tell anyone about it.
Once they've identified Tubbs as a violin storeowner, MacGyver and Lulu go to his shop. They break in and finds Izzy, but Tubbs and Ginko capture them at gunpoint. Tubbs has Ginko watch MacGyver and Izzy while he takes Lulu back to the party to get the Amadeus. Once they're gone, Ginko taunts the prisoners by setting some papers on fire with a lamp. Once he goes to the next room, MacGyver knocks the flaming papers into the wastepaper basket. That sets off the carbon dioxide extinguisher. MacGyver and Izzy hold their breaths while Ginko passes out. Once he's unconscious, they cut their ropes with a band saw, haul Ginko out of the room, and MacGyver leaves for the party.
At the party building, the band is packing up for the night when Lulu and Tubbs arrives. One of the violinists plays the Amadeus and Tubbs immediately recognizes it. He forces the band member to turn it over at gunpoint and then tries to escape as MacGyver arrives. MacGyver knocks out the cage elevator controls to keep Tubbs from escaping and the crook climbs up a fountain to make his escape. MacGyver and Lulu corner him and he threatens to destroy the Amadeus. Lulu says he must be the son of a cafeteria worker and figure he's stealing the Amadeus to make up for his childhood trauma. Distracted, Tubbs drops the violin and MacGyver catches it before it hits the floor.
Later, MacGyver and Wilt are out exercising when Lulu pulls up. She's now working as a driving instructor. MacGyver introduces Wilt to her and the two of them hit it off.