Late at night in San Francisco, a burglar carefully wipes his feet before breaking into a house. The man of the house, a sports agent named Rob Sherman, greets the burglar. The burglar is there as part of an insurance scam the two men concocted together. The burglar would "steal" some expensive sports memorabilia from the house, and the two men would split the insurance money later. But Sherman has a bigger plan, and surprises the burglar by pulling out two guns. Sherman shoots the burglar with one gun, and when Sherman's wife comes downstairs, he shoots her with the other gun! Sherman then calmly arranges the scene before calling 911.
The next morning, Monk and Natalie join Stottlemeyer and Disher at the house to investigate. Rob Sherman tells his story. He was in bed. His wife woke up and went downstairs to adjust the thermostat. He heard a gunshot. He grabbed his gun and went downstairs where he found the burglar, whom he'd never seen before, and his dead wife. He shot and killed the burglar in self-defense.
It seems like a routine case, but for Monk, things don't add up. Monk can't understand why the burglar would leave footprints on the patio, but then take care to wipe his feet before coming inside. Just as Monk notices this, Sherman tells Monk to wipe his feet, and in so doing, immediately becomes the focus of Monk's attention. Monk searches the house and finds clues that call Rob Sherman's entire story into question.
Meanwhile, Julie Teeger and her boyfriend, Tim, are outside waiting for Natalie. Rob Sherman approaches. He's noticed Julie's T-shirt, which features a romantic photograph of Julie and Tim. Sherman asks where the photo was taken, and Julie explains that it was taken at the Bay City Pier amusement park.
Later, Monk, Natalie, Stottlemeyer and Disher are discussing the case at police headquarters. Monk thinks that Rob Sherman and the burglar knew each other, which would explain why the burglar wiped his feet. But Stottlemeyer doesn't see a connection. The burglar was a career criminal, while the only thing on Rob Sherman's record was an arrest for driving with a suspended license. It's a good point, but after a little research, Monk learns that Sherman's day in court for his traffic violation just happened to be on the same day as the burglar, Dewey Jordan, was in court for one of his many crimes. Monk theorizes that Sherman and Jordan met on that day, but when confronted with this theory, Sherman continues to deny ever seeing Jordan before the night of the robbery.
Back at Natalie's house, Natalie and Julie get into an argument. Julie has broken up with her boyfriend, Tim, and has started dating Clay Bridges, a star football player at Julie's high school. Natalie wants Julie to stay with Tim, but an angry Julie defiantly burns all reminders of her relationship with Tim, including her special photo T-shirt.
Later, at Dewey Jordan's apartment, Natalie accompanies Monk as he snoops around. Monk finds a small handgun and some ammunition, and wonders why Jordan didn't bring this gun to the robbery at Sherman's house. And if the gun used to kill Rob Sherman's wife belonged to Jordan, why is there no ammunition to match that type of gun anywhere to be found? While Monk ponders these questions, Natalie, desperate for help with Julie, convinces Monk to talk to her daughter. Monk may seem like an odd choice, but Natalie insists that Monk's devotion to Trudy makes him well qualified to talk about relationships.
Monk has an awkward talk with Julie that seems to help, but just when Natalie thinks everything is under control, she and Monk discover Clay Bridges kissing another girl on the street. Clay confesses that a woman claiming to be Natalie's sister hired him to woo Julie. Suddenly, everything makes sense to Monk! He and Natalie take off for the Bay City Pier.
While they're waiting at the pier for Stottlemeyer, Monk and Natalie spot Tim, who works there. A moment later, Monk spots Rob Sherman, who's apparently been alerted by Clay that Monk and Natalie are on to him. As Monk chases Sherman around the pier, Natalie explains everything to Tim: Rob Sherman and Dewey Jordan met at the Bay City Pier to hatch their insurance scam on the same day Julie and Tim got their picture taken. The two men wound up in the background of the photo, and when Sherman saw the picture on Julie's T-shirt, he knew it was only a matter of time before Monk or the police spotted them on the shirt as well. If the police could prove that the two had met, they could prove that the robbery was a sham and that Sherman had concocted the whole thing as a way to kill his wife. So Sherman had his mistress hire Clay to get between Julie and Tim, so Julie would stop wearing that incriminating T-shirt. The plan would have worked if Natalie hadn't spotted Clay on the street, but now Sherman has no choice but to come to the park and steal any remaining copies of the photograph.
With Monk chasing him, Sherman finds the photo booth where the incriminating picture was taken. Sherman wrests the relevant photo disks away from a clerk and dumps them into the ocean before Monk can stop him. With the photo disks ready to sink, it looks like Sherman will get away with murder. Just then, in an uncharacteristic show of bravery, Julie's ex-boyfriend Tim jumps off the pier and rescues the disks!
Rob Sherman is arrested. Tim emerges from the ocean as a hero, and wins back Julie's heart, much to Natalie's relief. And Monk shows that he can be a great detective while playing cupid to a pair of teenagers at the same time.