As attorney Lou Pratt finishes his day's work, a shadowy figure creeps into his office, kills the luckless attorney, then removes and burns a file from the file room. It's not long before Monk is called in to assist with the investigation.
The prime suspect: Lawrence Grayson, the client whose file was burned in Pratt's office. At Grayson's home, Monk learns that not only did Grayson owe the dead attorney money, but that he had also threatened Pratt one year earlier, after Pratt failed to win an injunction to keep Grayson's neighbor, the lovely Monica Waters, from building a garage near Grayson's property line.
Monk can't believe that a petty legal dispute over a simple garage could turn so deadly. He also can't believe the striking resemblance between Monica Waters and his late wife Trudy. Monk is smitten, and he arranges to have dinner with Monica to discuss the case. However, it's clear Monk is more interested in Monica than in the murder.
Later, at Pratt's funeral, one of Pratt's elderly clients keels over dead after Monk berates him for coughing. The old man's nephew shouts at Monk for his heartlessness.
Stottlemeyer is convinced of Grayson's guilt - that is, until Grayson is found murdered in Monica's garage. Suspicion now falls on Monica, who Monk refuses to believe is a killer. Stottlemeyer and Sharona fear that the love-struck Monk is putting himself in harm's way. Their fears are confirmed when they learn Monica's husband has been missing for several months and is presumed dead.
Determined to clear Monica's name, Monk and Sharona return to Pratt's office, where all the clues finally click into place. At the reading of a family will, Monk reveals his discovery: neither Monica nor Grayson were responsible for Pratt's death. Surprisingly, the culprit was the nephew of the old man who dropped dead at Pratt's funeral. The nephew, Todd Katterskill, knew he was going to be excluded from his elderly uncle's will, so he broke into the office of his uncle's lawyer, Lou Pratt - not to destroy anything in the file room, but to leave something behind: a new, forged will which left everything to him.
Pratt had to be killed because only he would be able to identify the will as a forgery. The file that Katterskill burned was chosen at random simply to send the police in the wrong direction, and Grayson was then killed to keep the police going down that false trail. As always, it would have been the perfect crime... if not for Adrian Monk.