Monk suspects that the man responsible for the mail bombing murder of rich and beautiful Amanda Babbage is the victim's brother, Brian – who has been in a coma for four months after attempting to lure Stottlemeyer and Disher into a car chase and crashing into two cars. Since the package was postmarked three days before the bombing, Stottlemeyer is naturally skeptical, but he prefers siding with Monk to tagging along behind Agent Grooms of the Bureau of Alcohol, Tobacco, and Firearms, who suspects the victim's other brother, Ricky.

As Monk and his friends watch a TV news magazine piece on the solution of his hundredth case, he realizes that one of the victims was murdered by a different killer.