Bart believes he witnessed Ned Flanders murder his wife. Lisa’s popularity soars after her family buys a swimming pool during a heat wave.
A heat wave hits Springfield, making the city’s “Pool Mobile” a popular attraction. Their appetite whetted after spending a few hours in the water, Bart and Lisa lobby Homer for a swimming pool of their own. Homer concedes to their demand, but the moment the pool is installed, children from around Springfield invade the Simpsons’ backyard. When Bart attempts an ambitious dive from the roof of his tree house, he loses his balance and falls, breaking his leg.
The cast on his leg prevents Bart from enjoying the new pool. He takes refuge inside his bedroom, where he remains isolated in darkness. Lisa feels sorry for her brother; her popularity has soared since the pool was installed, but she realizes Bart is lonely and bitter. She gives him her telescope, hoping it will help him fill the time. Using the telescope to spy on his neighbors, Bart notices Ned Flanders digging a grave in his backyard while muttering about killing his wife. Bart concludes that Flanders is a killer.
Lisa’s popularity plummets when Martin’s family installs a much bigger pool in their backyard. Realizing she has been neglecting her brother, she apologizes to Bart for ignoring him and promises to help gather evidence that will prove Flanders murdered his wife. When Flanders drives away from his house with his children, Lisa sneaks inside. Bart watches from his bedroom as Ned returns shortly afterward carrying an axe. Horrified, Bart hobbles across the lawn to warn his sister. Lisa spots Flanders and hides in the attic. Flanders makes his way to the attic and poises his axe as if to strike. Bart suddenly appears and stops Flanders. He accuses him of killing his wife. But Flanders explains that what he murdered was his wife’s favorite ficus plant—a plant he was supposed to take care of while she was away at Bible school. He admits he buried the ficus in his backyard. His story seems all the more credible when Maude Flanders appears safe and unharmed.
Source: 20th Century Fox