Monk and Natalie stop by Captain Stottlemeyer's office during his nightly webcam date with his girlfriend, Linda Fusco. Meanwhile, Linda's real estate partner, Sean Corcoran, is out of town showing a house to a young couple. Suddenly, an intruder appears. Without saying a word, the intrude shoots Sean Corcoran dead, but allows the terrified couple to escape with their lives. The next day, Linda hears the devastating news that her partner has been killed. Stottlemeyer promises to find the killer and sends Monk to the crime scene to investigate. Monk deduces that the killer had a key to the house and a witness recalls that the killer was wearing lipstick, so perhaps the perpetrator was a woman Later, Linda reveals that Sean Corcoran had a female enemy named Helen Hubbert. Hubbert had been writing Corcoran threatening letters after she became unsatisfied with a house he sold her. However, after Monk finds the same shade of lipstick the killer was wearing in Linda's purse, he has another suspect in mind – Linda Fusco.