Monk is vacuuming when his vacuum cleaner jams. He tries to clear it and hears someone knocking on the door. Monk tells them to call in, assuming it's Natalie, and then the dust gets in his eyes. Sharona comes in and comes to his aid, and once he cleans the dust out, he realizes that his old assistant is back.
Monk double vacuums up the dust and asks Sharona where his shirt is from the Friday before she left. He wants to look through her purse and she shows him a picture of Benjy. Monk wants to know if he's at home where he can find the cleaning ticket. Sharona finally gets around to explaining that she returned to nursing and separated for good from Trevor. When she finds his wipes for him, Monk assures her that she still has it. Natalie arrives and Monk hastily introduces Sharona and assures her that nothing is going on. Sharona explains that she's there for a couple of days because her Uncle Howie died and she's the only family he had. He died at the Eastdale Country Club after falling down a flight of stairs. It's the club's fault so she's meeting with her lawyer to sue them. Sharona suggests they go with her and then they can have lunch afterward. As they leave, Natalie realizes that Monk paid Sharona more than he pays her.
At the lawyer's office, Natalie wants to know why Monk paid Sharona more. He agrees to pay Natalie the same as long as Natalie doesn't compare notes. Meanwhile, the country club's lawyer makes Sharona an offer but her lawyer insists that Sharona isn't there to be insulted. Sharona sees what they're offering and accepts. Monk and Natalie go in to see Sharona, who explains that the offer is enough to play for Benjy's college. She admits she wasn't that attached to Howie. However, Monk notices the photos of the accident on the wall and realizes that there's something wrong. Sharona warns that if it wasn't an accident, the club doesn't have to pay, but Monk can't let it go.
Monk, Natalie, and Sharona go to the golf course and meet the golf pro, Perry Walsh. He's playing with his wife Carolyn. Walsh introduces his caddy Gary Hanks and Sharona explains that she's the niece of the dead man. Perry and Gary saw the accident and both confirm that they saw Howie fall down the outdoor stairs. Gary's cell phone was dead so he went for help while Perry tried to revive Howie with CPR but to no avail.
Monk goes to the crime scene and examines the stairs. He asks Sharona to lie on the ground. When she refuses, he asks Natalie, who also refuses. Monk admits that the step is loose and it must have been an accident. However, once Sharona steps away, Monk tells Natalie that it was murder. He's concluded from the photos that the photos and time schedule indicate that Howie couldn't have been playing golf when he died.
Sharona goes to the station to see Stottlemeyer and Disher. Disher wonders when she's going to insult him and admits that he looked forward to it. Natalie and Monk come in and get the rap sheet on Howie, who has no previous convictions. However, he was involved in two similar lawsuits where he settled out of court in both instances. Sharona wants Monk to tell her the truth and Natalie forces him to suggest that they should check out Howie's apartment. Stottlemeyer talks to Monk in private and suggests that he not talk Natalie and Sharona together. He warns that they'll drive him crazy because they don't mix, but Monk can't choose.
At Howie's apartment, Monk finds a lot of past-due bills indicating that Howie was broke. He also finds cushions stacked up on the kitchen table and realizes that Howie was practicing falling. Howie staged an accident so he could sue the country club but Sharona insists that he's not wrong and the evidence doesn't mean anything. She suggests that they go back and talk to Perry, and Natalie accuses her of only worrying about the money.
Sharona returns to the police station and wants to talk to Disher. She explains that she always used to feel better after talking to him and tells him about Monk's theory. Disher notes that Monk is always right but Sharona thinks Natalie has turned Monk against her.
As they go to see Perry, Sharona accuses Natalie of pandering to Monk by taking the stairs. They eventually take the elevator and then walk down the stairs. They get to the Walsh apartment and Monk asks if he saw Howie played any golf the day of his death. Perry admits that he didn't, but Monk is more interested in the fact that Carolyn has a series of books and one of them was at Howie's apartment. He asks for some water and once Perry goes to the kitchen, Monk points out the clue and figures that Carolyn was having an affair with Howie and Perry discovered it. Sharona insists that Monk explain what happened. Perry found about the affair, kept it a secret, and then planned his revenge. Monk worries that Perry can hear them, so Sharona ushers them into a closet and Monk rushes through the explanation. When they can't understand, Monk explains that Perry went to Howie and offered to help him set up the fake fall for the lawsuit. On the day of the murder, Howie faked the fall. Gary went to get help and Perry then slammed Howie's head into the stone stairs, killing him. Perry opens the door and they realize that he knows everything. Perry tells them to leave.
Monk goes to Stottlemeyer, who isn't happy that Monk explained everything. Now they don't have a case and Perry has lawyered up. However, Stottlemeyer warns that they have no physical evidence and Natalie insists it isn't her fault. Everyone starts arguing about whose fault it is and Monk slips away. He goes outside and hails a taxi to go as far away as he can.
At Monk's apartment, Natalie and Sharona worry and wait, but Disher and Stottlemeyer have no news. They start to bond and Sharona wonders how either one of them ever put up with him. She admits that she loved him and every day was an adventure. They both apologize to each other and Natalie admits that Sharona was there during the worst times right after Trudy died.
Sharona and Natalie find Monk at Trudy's grave and tell him that they're fine. Sharona now agrees that they have to nail Perry and bring Howie's murderer to justice. They take him back to the country club to look for clues. Sharona breaks into Perry's office and they go through his desk. Monk finds a lithium cell phone battery and realizes it's the same model that Gary owns. He realizes that Perry switches batteries so Gary would have to leave to get help. Monk realizes that the new battery in Gary's cell phone will have Perry's fingerprints on it. Perry overhears them and runs out to get the cell phone. Monk chases after him and Natalie and Sharona borrow a golf cart. Perry finally stops and then punches Monk. Natalie and Sharona drive after him and Sharona leaps off and tackles him. Working together, they finally knock him out and go to get Gary's phone. As they go down the stairs, Sharona stumbles on the same broken step and breaks her arm. She realizes that she'll get the settlement money after all.
Later, Sharona is saying goodbye to Monk and Natalie and assures them her friend is picking them up. Sharona says she'll sleep a lot better now that she knows he's in good hands. Her ride pulls up and Sharona gives Monk a hug. She tells him she'll be back in a couple of weeks to file the lawsuit and tells Natalie to call if she has any problems. Sharona then gets in the car with... Disher, after exchanging a kiss.