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.
While investigating a murder, Stottlemeyer gets into an argument with a cop at the scene who snidely tells him he has been seeing his wife. As a result the crime scene was deemed contaminated. He later asks Monk to follow his wife to see if it's true.
Lt. Disher and Captain Stottlemeyer capture a "Most Wanted", Columbian criminal, Miguel Escobar, who's wanted for drug trafficking crimes in multiple states, and arrest him for a local homicide. Escobar is notorious for escaping custody, so Stottlemeyer must take extra precautions to ensure that this does not happen while Escobar is in his custody. Captain Stottlemeyer learns that the US Attorney General is ordering him to turn over Escobar to the Federal Government, and is to do nothing more than detain their prisoner until the hand-off, following an extradition ...