S6E1: Bart of Darkness

In the first episode of season 6, "Bart of Darkness," Bart breaks his leg and ends up stuck inside the house with nothing but a telescope for entertainment. Naturally, this leads him to suspect that their neighbor, Ned Flanders, has committed a murder. Bart becomes convinced that Ned has killed his wife, Maude, after witnessing some suspicious behavior and hearing what he thinks is a confession. He ropes in Lisa to help him investigate further. As these things go in Springfield, it all escalates until Bart decides he must sneak into the Flanders' house to find evidence. Of course, he gets caught by Ned himself, who turns out to be... perfectly innocent. The "murder" was just a misunderstanding involving Maude going away and Ned's clumsy attempts at keeping her secret surprise party under wraps. So, no murder — just another day in the Simpson household.