When Julie's high school basketball coach dies in an apparent accident, Julie and her friends from the basketball team suspect that their coach has been murdered, and they want to hire Monk. Monk takes the case, and he and Natalie go to Julie's high school to investigate.
The coach, Lynn Hayden, was killed in the team locker room when she stepped into an electrified pool of water caused by a carelessly placed towel, a leaky drain, and a fallen hair dryer. But after some snooping, Monk suspects that the girls are right, and that this so-called accident was really the work of a killer.
But who would want to kill the girls' beloved basketball coach? Monk and Natalie talk to the school principal, who mentions that the coach had seemed troubled recently, but that she had no obvious enemies. When the conversation turns to basketball, the principal reveals plans to cancel the girls' upcoming championship game. Natalie volunteers to coach the team, and makes Monk her assistant coach.
Monk continues to work on the case while he helps Natalie with the team, and soon, he makes a crucial deduction. A couple of weeks before her death, Coach Hayden started a forest fire while on a hiking trip. Monk and Natalie talk to Coach Hayden's brother, Aaron, who confirms that she did indeed start the fire, and that she was planning to go to the authorities to confess, despite his protestations. Monk suspects a connection between the forest fire and the coach's death, but he doesn't know what it is.
Soon, it's the day of the big basketball game. Natalie stalks the sidelines with Monk at her side, as the girls play their hearts out on the court. After an argument with a referee, Natalie gets ejected from the game, leaving Monk to coach the team. While Monk coaches, Natalie notices something in the girls' locker room. A photo of Coach Hayden that was donated to the school by her brother has been repaired with a piece of tape, and the tape has a distinctively frayed edge, a frayed edge similar to one which was found on a piece of tape on the hair dryer that electrocuted Coach Hayden! Natalie rushes out to the basketball court to share her discovery with Monk. They confer, and quickly come to the conclusion that Coach Hayden was killed by her own brother!
Here's what happened: Three years ago, Coach Hayden's brother killed a girl at a country club, and left DNA evidence at the scene of the crime. Fortunately for him, the police had nothing to match the DNA against, and he never came up as a suspect. But if Coach Hayden went to the police about the forest fire, her DNA would be taken, and the similarity between the siblings' DNA would lead the police back to the country club murder. Coach Hayden's brother couldn't let her go to the police, so when she insisted on confessing, he had to kill her.
The brother, who is at the game, is quickly apprehended by Stottlemeyer and Disher, who are also in attendance. The girls end up losing the game, but with Monk's help they earned a greater victory by preventing a criminal from getting away with murder.