Monk is having a hard time finding a new assistant, and Natalie might be just what he is looking for. But first he has to take her case and solve the mystery of the intruder who seems inordinately interested in her daughter's pet fish.
When an author of a book debunking the career of a popular martial-arts movie star is killed, the evidence points to the star himself, despite the fact that he has been dead for years! Monk takes the case and also gets a chance to prove to Natalie that he is not as selfish as he seems.
As sole witness to a murder, Monk is shuffled off to a safe location until he can give a deposition. When a man is killed by lightning while fishing on the lake outside his cabin, however, Monk believes there's more to the man's death than meets the eye.
A motley assortment of commuters, including Monk and the gang, are stuck on the highway after a fatal car accident brings traffic to a dead halt. But Monk doesn't think it was any accident and his impromptu investigation irritates authorities at the scene.
On Halloween, Monk visits his brother Ambrose in his childhood home to await a visit from his long-absent father, but things take a strange turn when a masked trick-or-treater repeatedly tries to steal Halloween candy from Ambrose's house.
When Natalie finally catches up with the pizza guy who mistakenly left her $50 in change, she finds him dead in his car. She feels compelled to solve the murder but Monk, sick in bed, offers little help.
Monk goes undercover as an office worker and revels in the office routines and actually starts making friends and a possible romance as he tries to solve a murder that occurred in a parking garage next to the office building as well as who injured the hand of the man who hired him whose hand was slammed into a car door probably by the murderer. But Monk's new found popularity may come to a screeching halt if he won't put on the pair of used bowling shoes for the showdown match between his office team and their rival team.