Hotheaded police detective Adam Kirk agrees to meet a mysterious informant named John Gitomer on a moving Ferris wheel high above a local carnival. Moments after the ride begins to move, however, Gitomer starts screaming in agony. The Ferris wheel operator brings the ride to a halt, Detective Kirk leaps out, and he turns to find Gitomer with a knife in his heart. Now the informant is dead - and no one but Kirk could have done it. Captain Stottlemeyer, Kirk's former partner, is determined to clear Kirk's name. But given the overwhelming evidence against Kirk, as well as his recent history of violence (he's currently being sued by a felon named Leonard Stokes on brutality charges), doing so may prove difficult. Fearing the worst, Stottlemeyer has no choice but to bring in Monk.
Monk, meanwhile, is facing a series of police review hearings in an effort to get his badge back. His first appearance goes well, and Monk is on top of the world when Stottlemeyer contacts him about assisting with the Kirk case. Though skeptical about Kirk's innocence, Monk agrees to help him. His investigation first takes him to the crime scene, where Monk's fear of heights prevents him from actually riding on the Ferris wheel. However, Monk is able to interview the eccentric Ferris wheel operator, and then he finds a valuable clue: a discarded claim ticket which fell from Gitomer's pocket during his fatal ride.
The ticket leads Monk and Sharona to a local dance club, and then to the checked item: a knapsack containing Gitomer's cell phone, on which is found a record of several phone calls made to none other than convict Leonard Stokes. Stokes, who always maintained his confession to Kirk was beaten out of him, is being let out of prison now that Kirk is facing murder charges.
After assembling all the clues, Monk figures out what happened: Stokes was the mastermind. His goal: frame Detective Kirk and ruin his credibility. His plan: hire his old friend Gitomer to pretend to be beaten up by Kirk on the Ferris wheel. What Gitomer didn't realize, however, is that Stokes also hired another, more ruthless accomplice - the Ferris wheel operator - to take the set up one step further and kill Gitomer as he exited the Ferris wheel, thereby framing Kirk for murder. Another perfect crime foiled by San Francisco's defective detective, Adrian Monk.