Paul Buchanan is a spoiled, young billionaire who lives in his family's grandiose mansion. Paul's father and stepmother have died recently, and since then, he's been receiving a series of anonymous blackmail letters. Paul has figured out that the letters are coming from his butler, Stilson, and one day, Paul decides to confront him. Stilson apologizes and promises that it will never happen again. Paul draws a gun and shoots the butler dead to assure that it won't.
Later, Monk and Natalie are on a visit to Natalie's parents' house, when the conversation turns to their neighbor, the aforementioned Paul Buchanan. Paul grew up with Natalie and has long harbored feelings for her, but Natalie thinks he is a creep. Natalie's parents explain the circumstances of the recent deaths of Paul's father and stepmother. The couple was driving on a nearby country road when they had an accident. Paul's stepmother was thrown from the car to her death, but Paul's father survived. He immediately called 9-1-1, but suffered a heart attack while on the phone, dying just moments after his wife. When Monk questions some of the facts of the story, Natalie suspects foul play. She has a hunch that Paul Buchanan is somehow involved, and hires Monk to look into it.
Monk and Natalie go to the scene of the car accident, where something interesting happens. Natalie attempts to make a cell phone call, but she can't get a signal. If there's no cell reception at the accident site, how did Paul's father call for help the night he died? Convinced that a crime has been committed, Natalie decides to send Monk to the Buchanan estate to snoop around.
At the estate, one of Buchanan's employees mistakenly thinks Monk is a candidate for the newly vacant butler position, so Monk plays along. Monk interviews with Paul, who is impressed with Monk's extraordinary cleaning and organizational skills. Paul hires Monk on the spot, putting Monk in charge of an entire staff of servants. Before long, Monk becomes obsessed with his new responsibilities, holding his staff to exacting standards. He makes a great butler, and for a while, it appears that Monk has found his new dream job!
In the course of his duties, Monk learns something interesting. Since Paul's stepmother died before his father, Paul's stepsisters don't stand to inherit any of the Buchanan fortune. In addition, Monk comes across evidence of Stilson's blackmail letters, as well as an incriminating spot of blood on Buchanan's carpet. But Monk is obsessed with being a butler, and the clues don't register.
Later, Natalie shows up at the mansion for a big luncheon. During the meal, she excuses herself and goes off to poke around. In the garage, she comes across the mileage log for the car Paul's parents were driving the night they died. According to the log, Paul's father made it home safely the night of the crash! Natalie rips off the page and pockets it just before Paul finds her.
Before Natalie can leave the estate, Paul stops her. He knows she has the incriminating page from the mileage log, and he threatens to harm her parents unless she joins him on a hunting trip. Meanwhile, after the luncheon, Monk finally puts everything together and comes to the realization that Paul is a killer. By this time, Natalie has already left for the hunting trip with Paul, and Monk can only hope that he's not too late to help her!
Monk grabs a gun and sets out on a search for Natalie. He soon finds her in a secluded clearing, with Paul holding her at gunpoint. Monk fires a shot and orders Paul to drop the gun. With the situation under control, Monk explains what happened. Paul found his father dead of a heart attack and realized that his stepmother would soon inherit everything and cut him off, so Paul quickly devised a plan. He killed his stepmother and staged the whole car accident so it would appear that his stepmother died first. Stilson the butler knew what Paul had done, and tried to blackmail him. When Paul figured out it was Stilson, the butler had to die, too.
Paul would have gotten away with his crime if not for the intervention of Monk and Natalie. With the case solved, Monk leaves behind his life as a butler, and returns to his true calling - solving crime.