Monk enters the world of high fashion when he believes a young man accused of a model's murder is innocent.

It’s late, and Monk and Natalie are at a deserted highway rest area. They’re there to meet a man who claims to have information about Trudy’s murder. Monk has brought an envelope of reward money, and he makes Natalie hide so he can meet the man alone. When the man turns out to be a phony, Monk refuses to give him the cash. A struggle ensues. The man clunks Monk over the head, steals the reward money and Monk’s wallet, and dumps Monk’s unconscious body on a flatbed truck. When Natalie reappears, Monk and the man are both gone.

Monk and Natalie join Captain Stottlemeyer at a junkyard to investigate the murder of a small-time drug dealer named Chicklet. While Monk looks around, a cocky young police sergeant named Ryan Sharkey implies that he's having an affair with the captain's wife, Karen. Stottlemeyer punches Sharkey in the face, and then leaves in a huff. Karen emphatically denies having the affair. The captain, still suspicious of Karen, asks Monk to follow her and find out whether or not she's having an affair.

Monk and Natalie go to police headquarters to ask Captain Stottlemeyer for a raise. While they are there, Lieutenant Disher brings in Warren Landis, a security guard from a local museum, for questioning. The world-famous Alexander diamond has been stolen from the museum, and the police are interrogating all museum employees. When Monk notices some chemical residue on Landis' fingers, Disher arrests the security guard on drug charges. When Natalie hears that there's a million dollar reward for the diamond, she convinces Monk to use his detective skills to try to find the stolen gem.

Monk must solve a murder when the author of a biography about a famous astronaut is found dead.

Monk investigates when Lt. Disher thinks he sees his dentist commit a murder.