Monk's neighbor, Kevin Dorfman, is doing some accounting work for a magician named the Great Torini. Kevin finds an inconsistency in the books and heads to a theater where Torini is rehearsing with his assistant, Tanya. Kevin tells Torini that the airlines have been overcharging him for years - during his tours, Torini's equipment always seems to weigh more on his return trips. Torini tells Kevin to forget about it, and asks him to fill in for him at an upcoming performance, when Torini will be out of town. Kevin, an amateur magician, is thrilled at the prospect of performing and agrees immediately.
Soon, it's Kevin's big night. Just before Kevin is set to go onstage, a backstage phone rings. It's Torini and Tanya calling from Reno, and everyone gathers around to listen to the call on speakerphone. The couple has exciting news - they're getting married!
After the phone call, Kevin does his show, and it's a disaster. He can't get any of his tricks right, and the only applause comes from Monk and Natalie. After the show, Monk tries to find the dressing room to console Kevin, and is pointed in the right direction by a maintenance man. When Monk arrives backstage, he sees Kevin lying on the ground. He feels for a pulse, but gets nothing - Kevin Dorfman's been murdered!
At the funeral, Monk runs into Torini. While they're talking, Monk recognizes Torini as the maintenance man who pointed him towards the dressing room the night of Kevin's murder. But Torini claims he was out of town the whole time, and has a room full of people who heard him on the phone call from Reno as an alibi. When Monk visits Torini's house and accuses him of murder, the magician smugly hands Monk a written confession - which promptly burns up in Monk's hand. Torini's the guy, but Monk can't figure out how or why he did it.
As Monk and Natalie sort through Kevin's belongings, Monk has a breakthrough. He remembers Kevin talking about Torini's equipment weighing more on his return trips. Monk suspects that Torini has been smuggling drugs and killed Kevin when he started asking questions. Monk volunteers at Torini's next performance, and battles his claustrophobia to enter Torini's magic, zig-zag cabinet, where he uses a chemical test strip to swab the inside of a secret compartment. While still inside the box, Monk tells Torini and his audience that the test has turned up positive for heroin. Torini shuts him up and spins the cabinet. When he opens it again, Monk is gone!
When the police show up to investigate, Torini pretends to have no idea what happened. Meanwhile, Monk is tied up in the basement with Tanya, the assistant, keeping watch. While down there, a phone rings and Monk puts together how they pulled off the murder. Torini never went to Reno - he simply waited in the basement until Tanya placed the call from a Reno hotel. When the phone rang backstage at a prearranged time, Torini picked up the basement extension, creating the illusion that he was in the same room as Tanya. When Dorfman's act was over, Torini came upstairs dressed as a maintenance man, and killed him.
Just as Monk finishes his summation, Torini comes downstairs to finish him off. Monk puts up a struggle, but it's only a matter of time before Torini overpowers him. Upstairs, Stottlemeyer discovers a trap door leading to the basement room. Stottlemeyer, Disher, and Natalie come bursting into the room just in time. They've got Torini red-handed.
A week later Monk and Natalie watch Kevin Dorfman's video will. In his inimitable way, Kevin rambles on and on and on, never getting to the point. And Monk and Natalie watch every minute of it.