After an armored car heist, Monk and Natalie arrive on the scene to join Capt. Stottlemeyer and Lt. Disher in the investigation. Two drivers were killed, and the thieves made off with millions of dollars in negotiable bank certificates.
While Monk picks up clues, Lt. Disher complains of a horrible toothache. Capt. Stottlemeyer insists that Lt. Disher visit a dentist immediately.
Lt. Disher goes to the office of Dr. Oliver Bloom, and soon finds himself under sedation while Dr. Bloom extracts a tooth.
Then, something strange happens: while floating in and out of consciousness, Lt. Disher sees - or thinks he sees - Dr. Bloom and his assistant kill an intruder after arguing with the intruder about the baseball player Barry Bonds.
As the armored car investigation continues, Lt. Disher tells Capt. Stottlemeyer about what he saw at the dentist's office. But the captain doesn't believe him. Nobody does. He must have been hallucinating from the anesthesia.
Convinced he saw his dentist kill somebody, Lt. Disher asks Monk to investigate. Monk, who has a severe fear of dentists, reluctantly agrees, and goes with Natalie and Disher to Dr. Bloom's office.
Before they can find anything, they get a call from Capt. Stottlemeyer. He's found a dead body that appears to be one of the hijackers from the armored car robbery.
When they arrive at the scene, Lt. Disher immediately recognizes the dead man as the intruder who was killed by Dr. Bloom. But once again, nobody believes him.
Frustrated at not being taken seriously, Lt. Disher quits the force and reunites his high school rock band, The Randy Disher Project, with dreams of becoming a rock star. Meanwhile, across town, Dr. Bloom is planning to kidnap Monk.
Lt. Disher was right!
Bloom sends his assistant to Monk's house, where she knocks him out with chloroform. When Monk wakes up, he finds himself strapped into an examination chair in Dr. Bloom's office. Monk notices a large model of a tooth, with roots that are about ten inches apart, on a nearby counter. Monk solves the case!
Here's what happened: One of the armored car hijackers injured a tooth during the heist, and went to Dr. Bloom to get it fixed. While the crook was under anesthesia, he talked about the heist and where he hid the stolen bank certificates. Dr. Bloom and his assistant saw an opportunity, and snatched the loot from the hiding place.
When the hijacker realized the certificates were gone, he figured out what happened, and confronted Dr. Bloom while he was working on Lt. Disher. A struggle ensued, just like Lt. Disher described, but they weren't talking about Barry Bonds, they were talking about the stolen bearer bonds. When the dead hijacker was found, he had bruises on his body that were ten inches apart. He must have been beaten with the tooth model!
Unfortunately, Monk is still strapped in Dr. Bloom's dental chair, and Bloom plans on torturing Monk until he tells him if the police know about a possible fence for the bearer bonds. It promises to be a horrible experience for Monk, but fortunately, Lt. Disher has also solved the case, and he and Capt. Stottlemeyer arrive just in time to save Monk and arrest the nefarious Dr. Bloom.
In the end, the killers are caught, Lt. Disher is back on the force, and Monk has a brand new reason to fear dentists.