Millionaire Las Vegas casino owner Daniel Thorn is leaving for a fundraising benefit with his beautiful wife, Sheryl, when tragedy strikes. Sheryl's trademark scarf gets caught in the doors of Thorn's private elevator, strangling her and breaking her neck. The authorities classify the death as an accident.
Captain Stottlemeyer is in Las Vegas for a bachelor party at the same time as the death. He suspects Sheryl Thorn was murdered, and calls on Monk to investigate. When Monk arrives, Stottlemeyer is too hung over from partying the night before to remember the incriminating evidence he discovered against Thorn, so Monk has to start from scratch.
Monk, Natalie and Stottlemeyer head to Thorn's private elevator, the scene of the "accident," where Monk spots some clues that seem to support Stottlemeyer's theory of murder. Monk and Natalie then catch up with Daniel Thorn at a groundbreaking ceremony, where they find another clue. Monk is convinced that Sheryl Thorn was murdered, but Thorn insists that his wife's death was an accident.
Soon, Natalie uncovers some important information: Daniel Thorn was having an affair with a dancer named Teresa Telenko. Monk and Natalie interview Telenko, who was suspiciously absent from work the night of Sheryl Thorn's murder. She denies any involvement, but it appears to Monk that Telenko and Daniel Thorn somehow conspired to kill Sheryl.
Determined to find a solution, Monk and Natalie return to the elevator and try to recreate Sheryl Thorn's death. Monk wraps a scarf around his neck, and watches the elevator doors clamp on the scarf. Then, to his surprise, the elevator starts up. Monk is being strangled, just as Sheryl Thorn supposedly was! Natalie cuts him free just in time for the elevator doors to open on Daniel Thorn in his penthouse, staring down at them angrily. Monk can't speak, providing him with yet another clue: Sheryl Thorn was heard screaming for her life the night she died. But how could she, with a scarf choking her to death?
Monk is getting close to an answer, but he soon gets pulled in another direction: Lieutenant Disher, in town with Captain Stottlemeyer, has been on a long losing streak at the blackjack table. Monk, who can count cards, decides to help Disher win his money back. When Monk can't lose, Daniel Thorn arrives to oversee Monk's gambling. Thorn, referring to his security network, reminds Monk that he has "friends hiding in the ceiling." Eureka! Monk has solved the case!
Monk explains: Thorn and his wife were heading to a fundraiser. They left Thorn's penthouse together, but Sheryl never made it out of the elevator alive. Once the elevator doors closed, Thorn and Teresa Telenko, who had been hiding on top of the elevator (friends in the ceiling!) killed Sheryl, then lifted her body through the access panel. Moments later, Telenko, now posing as Sheryl, made it appear in front of witnesses as if her scarf got caught in the elevator doors. That was only a diversion: what Telenko really did was return the dead body of Sheryl Thorn to the elevator floor while she escaped through the ceiling access panel. When the elevator doors opened at Thorn's penthouse, Sheryl Thorn appeared to have been accidentally strangled to death by her own scarf.
It's another crime solved, this time in Las Vegas, where the house always wins... unless Adrian Monk is in town.