Former San Francisco Police Commissioner Harry Ashcombe's wife races along a winding highway on a dark, stormy night. Unbeknownst to her, the former commissioner has mysteriously placed a makeshift ramp in the middle of the road. Rounding a corner at high speed, Mrs. Ashcombe hits the ramp, and is sent flying over the hillside to her death. It's the perfect murder.
When Ashcombe puts out a call to help locate his "missing" wife, Monk and Sharona volunteer their assistance. But no sooner than they are on the case when the body of Mrs. Ashcombe is discovered by notorious quack psychic Dolly Flint, who claims she was led to the body in a psychic trance.
After attending the late Mrs. Ashcombe's memorial service, Monk begins to suspect that her death was more than just an accident. His suspicions soon lead him to one Jennie Zeppetelli, a young woman who he learns has been carrying on an affair with Harry Ashcombe for years until breaking it off when she began to fear for her safety. When Monk later questions Dolly Flint and learns that she has sleeping disorder, the pieces of the puzzle begin to fall into place.
Monk deduces that Ashcombe murdered his wife by sending her over the cliff to make it look like an accident. But an unforeseen mudslide caused a problem: with the car buried under the mud, no one would ever find his wife's body, and Ashcombe would never be able to claim the insurance money. Enter Dolly Flint: Ashcombe's plan was to drug Dolly and leave her at the crime scene, making it seem like her psychic powers had led her to the victim.
Now that Monk has pieced the puzzle together, he uses Dolly and Jennie to help set a trap for the shady commissioner. Staging the murder of Jennie, Dolly conducts a "seance" and leads the search party to Ashcombe's house. After being confronted with the seemingly dead body of his mistress, Ashcombe is tricked into confessing the truth, and once again Adrian Monk gets his man.