A former San Francisco police detective suffering from an extreme case of obsessive-compulsive disorder is called in to investigate an apparent assassination attempt of a mayoral candidate in which one of his bodyguards is killed.

With an introduction to Monk's talent, his phobia's, and need for an assistant, Monk investigates the murder of the candidate bodyguard and a political worker. He determines the candidate was not the intended target.

When a woman drives off the road to her death, her body is mysteriously found the next morning by a psychic known for fudging the truth. Monk must discover if she's telling the truth this time, or else let a murderer go free.

Upon being reinstated, Monk is put in charge of tracking down a serial killer.