Former college student Brett Reynolds and his group of high school seniors, Holly, Adam, and Jonathan, are drinking at a house where the residents are on vacation. The fifth member of the group is absent and they go to find her. It's Lisa Woodman, passed out drunk. Holly brought Lisa but admits she didn't have a choice. The maid pulls up outside, and Brett tells the others to meet him later at the Safari Gun & Travel Club. They leave, abandoning the unconscious Lisa, and Brett goes upstairs to grab the loot they've stolen from the residents, the Wilsons. The maid comes in and sees Brett, and he kicks her down the stairs. She lies unconscious at the foot of the stairs while Brett leaves.
Later, Captain Kelly calls MacGyver into the station and tells her they arrested a girl at the site of the most recent in a series of burglaries. The girl said she'd only talk to MacGyver. It's Lisa, who says she's on the outs with her parents and figured MacGyver would give her a chance. She lies to him and says that she knew the Wilsons were on vacation and their daughter Darlene invited her to stay there when Lisa was feeling ill. She claims she left the door unlocked, and the thieves must have gotten in that way. Kelly tells MacGyver that Lisa was drunk when they found her but Lisa claims that she had some candy cordials. MacGyver is skeptical, but Lisa insists she's never lied to him.
Brett meets the others back at his father's club. He complains about the fact that his father cut him off after he flunked out of Stanford. They hide the money from the Wilson robbery with the rest of the stolen goods. Brett asks Holly what happened to Lisa, and Holly admits that Lisa never came home. He tells Holly to talk to Lisa and find out what she might have told anyone. As he shoots targets at the range, Brett assures the others that if Lisa gave them away, he'll take care of her.
MacGyver takes Lisa home and talks to her parents, Eric and Katherine. They want to know what's going on, and Lisa accuses them of believing the worst about her. They know she skipped school and want to know where she was. MacGyver tells them that Lisa was arrested, and there'll be a hearing. Lisa insults her parents, who send her to her room. Once she's gone, they tell MacGyver that Lisa is missing school and getting low grades when she does show up. Meanwhile, Lisa stops in the kitchen and takes a drink from her parents' liquor supply.
MacGyver meets with Kelly at the Wilson house. The captain informs MacGyver that the Wilsons don't have a daughter named Darlene and have never heard of Lisa. Further, the arresting officer's report confirms that Lisa was drunk. The maid is in critical condition, and Lisa is the only suspect they have in the assault and the robbery.
At Lisa's high school, Holly tracks down Lisa and tries to find out what happened to her and what she told the police. Holly claims she had no idea that Lisa was left behind and denies her friends' involvement with the robbery. MacGyver arrives and offers Lisa a ride home. As they go back to his truck, he insists on learning what really happened. Lisa lies, saying she was drinking, went to the Wilson house where she found an unlocked door, and went in and passed out. When MacGyver worries that she has a problem, Lisa insists he has no idea what things are really like. He responds by describing how he tried drinking once, but didn't like the loss of control. The friend he drank with didn't have a problem, kept drinking, and five years later lost control of his car and crippled his girlfriend.
At the Challenger Center, MacGyver has Lisa take a 20-question test about her drug use. She lies again, filling in harmless answers, and goes home with MacGyver. While Katherine talks to her in private, MacGyver informs Eric that Lisa might have a drinking problem. Eric doesn't believe it, and MacGyver points out that parents are often the last to know. Katherine comes in with Lisa and informs her husband that Lisa has been forging Katherine's signature on credit card purchases of food for her new friends' parties. Eric tells his wife and daughter that MacGyver accused Lisa of being an alcoholic. MacGyver, angry, insists that's not what he said. Lisa storms off and both parents attack MacGyver. When he points out that some research has indicated alcoholism is sometimes genetic, they both believe he's blaming them and tell him to get out.
At the Safari Club, Brett uses his access to log onto the computer record and learn which members are traveling out of town so he knows the best houses to rob. Holly arrives and informs her boyfriend that she just now learned that he injured the maid. When he wants to know what she found out, Holly admits that MacGyver interrupted her chat with Lisa. Brett goes to talk to Lisa and find out what she told the police.
Lisa is slipping out when Holly and Brett pulls up. Brett suggests they go to the beach to party and skip school. He convinces a reluctant Lisa to come along.
MacGyver meets with Captain Kelly and asks for his help to figure out who Lisa is hanging out with. He figures her "friends" are the robbers. Kelly has the files on the robbery victims and is unable to find a connection, and MacGyver offers to help.
Brett, Adam, and Holly take Lisa to the beach and Brett tries to get her drunk so she'll tell him what he wants to know. Lisa refuses at first, saying she doesn't want to give MacGyver the satisfaction. Brett soon taunts her into drinking, suggesting she should be able to take one drink and stop if she isn't an alcoholic. Lisa gives in and takes the first bottle.
MacGyver reviews the victim files and discovers that they all made travel arrangements through the Safari Club. Homicide calls Kelly to inform him that the maid died, and Lisa is wanted for questioning. Kelly lets MacGyver bring Kelly in while he goes to the travel agency.
Several bottles of beer later, Lisa is drunk half out of her mind. Brett pumps her for information and learns that MacGyver isn't a cop. Jonathan arrives and tells Brett that the maid died. Brett assures him that he'll take care of everything. He tells Holly to get home but she's realized that something is wrong. He admits that the maid died and tells Holly that he plans to take care of Lisa. When Holly balks, Brett warns her that she's in as deep as he is.
MacGyver goes to see Holly and sees her leaving with packed suitcases. She refuses to cooperate with him and denies that Lisa is her friend. As she gets in her car, she drops a suitcase and MacGyver spots a photo of her and Brett at the Safari Club. He forces the reluctant Holly to admit that Brett's father owns the club and that Brett has full access. Lisa finally admits that Brett plans to eliminate Lisa.
Brett goes to the house of his next victims and finds their car keys. Adam and Jonathan bring Lisa with them to the House, and Brett claims that the house belongs to his uncle. One of them takes Lisa into the next room and waits until she passes out.
MacGyver calls Kelly at the Safari Club. The captain checks with the travel agent, who admits that Brett has access to all the files. She checks and discovers which file Brett accessed most recently and gives them the address.
Brett and his two friends take Lisa to the garage and put her in the owners' SUV. Brett turns on the SUV and lets the garage fill with carbon monoxide. He tells Adam and Jonathan to go to the club while he grabs the loot. MacGyver arrives at the house and goes inside, and Brett opens fire on him. MacGyver manages to evade him and then sets up a figurine and a light to make it appear that MacGyver's silhouette is on a decorative screen. Brett fires on it and MacGyver ambushes him.
Lisa wakes up and tries to get out of the SUV. She inadvertently puts the vehicle into gear and it smashes through the garage doors and out over a nearby guard rail. The SUV hangs by the guard rail a hundred feet above the surf. MacGyver gets there and tells Lisa not to move. He uses the guard rail chain to anchor the SUV just as it plummets over the cliff. It hangs halfway down the hill and MacGyver uses a length of chain fence as a ladder to climb down. He gets Lisa to climb partway out the window and then grabs her and pulls her to safety just as the chain breaks and the SUV falls into the ocean.
Later, Brett is taken away and Lisa finally admits to MacGyver that she lied on the test and she might have a drinking problem. He notes that admitting she has a problem is the first step in dealing with it.