Ralph Buchanan was an antique car dealer and a murder victim in Mr. Monk Is At Your Service. According to Natalie, Ralph was the most cautious driver she ever met because he wouldn't drive unless everyone had their seat belts on. One day, Paul discovered that his father had died of a heart attack in the garage and panicked. He had a problem; this would mean that Camilla would inherit everything and then pass it down to her daughters, leaving Paul with nothing. He conspired to make it look like Camilla had died first. He started by rushing over to Camilla, who was having tea at the time, and told her that there was an accident up the road. He drove her to a deserted road with Ralph in the trunk. When Camilla was turned around, Paul bludgeoned her with a rock, put Ralph's body at the scene, and attempted to call 911, but failed as there was no signal. He walked down the road and called 911 posing as his father (who he sounded a lot like), before pretending to have a heart attack. This way, it would seem like Camilla died in a car crash before Ralph's heart attack, thus making Paul the next inheritor.
His scheme succeeded, and Paul became the owner of Ralph and Camilla's estate. Adrian Monk and Natalie Teeger suspected something was amiss, given Ralph's reputation as a cautious driver. Moreover, the details of the car crash suggested he couldn't have made a call because of the weak cell phone signal at the location. Monk, who had unknowingly taken a job as Paul's new butler under the name Adrian Melville, connected the dots, uncovering the truth behind Ralph and Camilla's murder, and managed to rescue Natalie from being shot by Paul.