Commercial jingle writer Richard Parker and his wife, Priscilla, are invited to dinner by their new neighbors, Eddy and Kay Otis. At dinner, Eddy shares his philosophy that one needs a lot of money “pumping through the system” to be able to enjoy life to the fullest. When asked how to make that happen, he suggests investing in drug and alcohol rehabilitation clinics. While Eddy and Priscilla chat, Kay joins Richard at the piano, delighting him with her singing. After taking the Parkers on a weekend trip to South Carolina in his private jet, Eddy offers Richard $25,000 to pay off his outstanding debts. Sometime later, Richard accidentally drives his car into Eddy, who feigns severe neck and back injury. Eddy receives a $30,000 insurance settlement and gives $25,000 to the Parkers. As their friendship grows, Eddy proposes that he and Richard swap wives for a night, as the women would likely not care or know the difference. Richard refuses, and following a heated exchange, the men terminate their friendship. While Eddy and Kay host a Christmas party, Priscilla complains to Richard that something is lacking in their marriage now that the Otises are out of their lives. Although Richard regrets accepting the insurance money, Priscilla berates her husband for his complacency, and commends Eddy for his sense of adventure. Richard joins Eddy and his guests as they sing Christmas carols, and the Otises renew their friendship with the Parkers. Richard eventually agrees to swap wives with Eddy, but is plagued by guilt afterward. Following his morning jog, he notices police cars gathered outside the Otis home. Richard soon discovers that Kay has been bludgeoned to death with a baseball bat, and Eddy accuses him of the murder. In jail, Richard’s attorney, George Gordon, relates the coroner’s determination that Kay had sex with Richard within half an hour of her death. In addition, Eddy denies any plan to swap wives, claiming he was out of town when the murder occurred. Outraged over these developments and the trauma they have caused the couple’s daughter, Lori Parker, Priscilla files for divorce. Richard is released on bail and returns home for some personal belongings. He notices someone inside the Otis house and enters to find private detective David Duttonville, who is investigating a $1.5 million life insurance claim by Eddy. Duttonville asks Richard for information, explaining he has only one week to find “something solid” to refute the overwhelming evidence in the case. The detective also reveals that Eddy seems to be romantically involved with Priscilla. Later, Richard discovers that Kay is alive and singing under the name Olivia Kamen. Richard questions the staff of the nightclub where she last performed, but they have been unable to locate her. Richard shares the news with a skeptical Duttonville, and suggests exhuming the victim’s body. However, the body was cremated after being identified by both Eddy and a doctor. Richard is almost certain that the physician was Dr. Pettering, who falsified Eddy’s accident claim. He also suggests that Eddy hired someone to substitute for Kay as both Richard’s sex partner and the murder victim. Although neither Duttonville nor attorney George Gordon consider Richard’s story credible, the detective’s investigation reveals that Dr. Pettering was involved in both claims. Furthermore, Pettering partnered with Eddy and Priscilla in opening a rehabilitation clinic. Richard spies on Eddy and Priscilla, and later hides in her car while she is on an errand. After revealing himself to Priscilla, Richard says that Kay is alive and gives her an audiocassette of “Olivia Kamen.” At Richard’s request, Priscilla plays the tape for Eddy that evening. When Priscilla claims she received the cassette by mail, Eddy angrily concludes that Richard sent it. Afterward, Duttonville and Richard learn that Eddy made four telephone calls to Savannah, Georgia, the day he heard the tape. Tracing the number to the hotel where Kay now resides, Richard travels to Savannah and finds Kay singing in a café under her new identity. He follows her to her hotel room, where she reveals that Eddy instructed her to drive his truck to an out-of-town location to establish his alibi. Richard is summoned to the lobby on the pretext that Duttonville wishes to see him. Realizing too late that he has been tricked, Richard races upstairs to find Kay bludgeoned to death, and escapes seconds before police arrive. Eddy returns home from what Priscilla believes was a trip to Atlanta. Later, Priscilla discovers an airline ticket in Eddy’s jacket and absentmindedly places it in her purse. While Richard hides outside their home, police inform the couple of the killing in Savannah, warning that their lives may be in danger as well. Later that night, Priscilla looks at the ticket in her purse and realizes Eddy was in Savannah, not Atlanta. She attempts to escape in Eddy’s absence, but he is at the bedroom door barring her exit. As Richard makes his way toward the house, he discovers Dr. Pettering in Eddy’s car. Richard subdues Pettering, enters the house, and moves quietly upstairs toward the bedroom. Meanwhile, Priscilla is sprawled across the bed as Eddy lies in wait with an Uzi machine gun. Unable to contain his sense of triumph, Eddy whispers to Priscilla that his plan is a success and Richard is his “puppet.” The police will find her dead, presumably beaten by Richard with a baseball bat, and Eddy will kill him in what will appear to be self defense. As Eddy moves toward the stairs, Richard surprises him by crashing through the bedroom window. Following a brief struggle, Eddy corners Richard, but as he is about to fire, Priscilla bludgeons him from behind with a baseball bat. In the aftermath, Richard is cleared of all charges, and the Parker family moves into a new home, isolated from all neighbors.