When a minor earthquake rocks San Francisco, trophy wife Christina Rutherford seizes the opportunity to bludgeon her husband Henry to death with a handy marble statue. Afterwards, she topples a huge wooden display case onto his body so it will appear he died during the earthquake. It's a crime of opportunity. A perfect murder. Or so Christina thinks...
Sharona, who'd been helping Henry Rutherford organize a fundraising dinner at their local church, decides to make a condolence call on Christina, and brings the quake-rattled Monk along. As Sharona comforts the "grieving" widow, Monk pokes around the scene of Henry's "accident." He finds a thin layer of plaster debris covering the floor, but almost no debris on the back of the display case. He also notices that several paintings hanging on the same wall that the display case toppled from are barely disturbed.
Suspicious, Monk relates his findings to Stottlemeyer, but Stottlemeyer has more than enough to do in the aftermath of the quake to give Monk's dubious theory much attention. "It was an earthquake, Monk," Stottlemeyer barks, dismissing him with a wave. "Things fall down."
Meanwhile, Sharona's block has been cordoned off due to earthquake damage, and she won't be allowed back in her apartment for several days. Even her phone lines are disabled while the workmen make repairs, so she can't call home to retrieve her phone messages either. Frustrated, she stands outside the police barricade watching the men work - and meets tall, dashing Australian journalist Darryl Wright. If Darryl seems too good to be true, he is: Darryl is actually Christina's lover, dispatched by Christina to remain close to Sharona until she can return to her apartment.
With Monk in tow, Sharona temporarily moves in with her free-spirited sister, Gail. Darryl comes along too, and that night during dinner, Monk catches Darryl in several lies. But only the next day does Monk realize that Sharona is in real danger: a look at Christina's phone records, a missing set of keys from Gail's handbag, and the death of a gas company employee outside of Sharona's damaged building all complete the picture of a murder gone wrong.
Monk deduces that Henry was on the phone leaving a message for Sharona when the earthquake struck. He dropped the phone, but left it dangling off the hook - which meant that his own murder was recorded on Sharona's answering machine! Christina only noticed her error after she had murdered Henry, and she and Darryl have been trying to recover the incriminating answering machine ever since.
Before Monk can warn Sharona, Christina and Darryl get to her and lead her back to her building at knifepoint. Desperate to escape, Sharona brings her quake-damaged ceiling crashing down on top of them and tries to flee, but Darryl scrambles from the rubble and corners Sharona with a knife. With seconds to spare, Monk, Stottlemeyer and Lt. Disher arrive - just in time to stop him.
Murder following an earthquake seemed like the perfect plan. But the killers didn't figure on dealing with that other force of nature: Adrian Monk!