Kyle Fisher (Jon Favreau), days away from his wedding, welcomes his bachelor party weekend as a chance to break free from his control-freak, Bridezilla fiancée Laura (Cameron Diaz). Along with his best friend Charles (Leland Orser), his friends Michael (Jeremy Piven), and Boyd (Christian Slater), and Michael's brother Adam (Daniel Stern), they celebrate in a Las Vegas hotel room complete with drinking, drugs, and a stripper (Kobe Tai).However, trouble begins when Michael accidentally kills the stripper in the hotel bathroom after paying her extra money to have sex with her. Michael, in his sexual aggression, accidentally flings her across the bathroom and she hits the back of her head against a towel hanger, killing her instantly.A hotel security guard shows up to respond to complaints about the noise from the party. He starts to leave after the guys promise to quiet down but spots the hooker's body in the bathroom. He prepares to call the police but is killed by Boyd who stabs him with a corkscrew and prevents him from leaving the bathroom until he dies. Boyd takes charge of the group and devises a plan to dispose of the bodies by burying them in the desert. Everyone grudgingly goes through with the plan, but soon guilt and nerves begin to destroy the group.Upon returning from Las Vegas, during Kyle and Laura's rehearsal dinner, Adam cracks under the pressure, leading to a confrontation between Adam and Michael in the parking lot. The rest of the group breaks up the fight, convincing Michael to leave, but instead he decides to crash his Jeep into Adam's beloved minivan. Seeing his brother's intentions, Adam darts in front of the Jeep at the last moment and is crushed in the collision.At the hospital, Adam whispers something to his wife, Lois (Jeanne Tripplehorn), before he dies. Soon afterward, Lois calls everyone over to her house. Lois states that Adam mentioned that something had happened in Vegas, but died before he was able to tell her. Seeing Michael in a state of despair, Lois prods him for information, threatening to call the police if she is not told the truth. As Michael is about to crack, Kyle quickly makes up a story about Adam having sex with a prostitute in Vegas. Lois appears to believe him, and the group leaves.After dropping Kyle, Michael, and Charles off at a nearby bar, Boyd returns to Lois' house, where a violent fight ensues after Lois realizes that Boyd intends to kill her. After they struggle, it is implied that Boyd succeeds in killing Lois. Immediately afterwards, Boyd calls Kyle, telling him that Lois wishes to speak to Michael. Kyle and Charles then take Michael to Lois' house, and, moments after Michael goes inside the house, a loud noise is heard and Boyd enters the car without Michael. Boyd then concocts a false love triangle story to explain Lois and Michael's deaths, in case any of the remaining three friends are questioned by the police.The next day, Kyle and Laura discover that they have been awarded custody of Adam and Lois' two disabled sons and their dog. This angers Laura, but even more so after they learn that Adam's life insurance policy is only worth $14,223. This new stress proves to be too much for Kyle, who confesses to Laura what happened in Vegas. Instead of being horrified at the confession of the murders, Laura is enraged that there is yet another distraction from her wedding, dismissing his confession.On the day of the wedding, Boyd confronts Kyle about Adam's insurance money. Kyle attempts to tell Boyd that there was no money, but Boyd attacks and begins strangling him, only to be bludgeoned from behind by Laura, knocking him unconscious. During the wedding, it is discovered that Boyd had the rings for the ceremony. Charles goes to retrieve them as Boyd is crawling up the stairs towards the wedding hall, leading Charles to inadvertently knock Boyd down the stairwell. Reaching into Boyd's coat for the rings, Boyd once again wakes and grabs his hand. However, he quickly loses consciousness and dies, as Charles retrieves the rings and rejoins the ceremony, which ends without further incident.Later, Kyle attempts to talk to Laura about his confession and is horrified to hear that she wishes more loose ends were tied up, ordering Kyle to kill Charles. She also orders him to kill Adam's sons and their dog to rid her of her responsibilities towards them. Kyle takes Charles, the dog, and a suitcase containing Boyd's body back out to the Vegas desert. After burying Boyd, Kyle appears to be preparing to bludgeon Charles with his shovel, however, the next scene shows them all driving back from the burial site. On the way back, Kyle loses focus while daydreaming, crashing head-on into an oncoming car.Some time later, Laura is scrubbing and cleaning her house, living the life she always detested. Kyle, Charles, the dog, and one of Adam's sons are now all disabled in some way and rely on Laura to take care of them. Kyle has lost both of his legs and is now a paraplegic; Charles is a quadriplegic; and the family dog now has only three legs and one eye. Laura, distraught over the pressures of all her unwanted responsibility, runs out into the street and falls down, crying and shrieking in anguish at this fate worse then death that she has landed into for the rest of her miserable life.