Bart is running around the yard declaring he is a sociopath. He later reads a book, and it tells him he can't do some things, but Bart takes that as a challenge. He proceeds to do what Donny doesn't do. Knife goes in, guts come out. The family is shocked by his actions and Bart is taken to a mental hospital. Later that year, Bart is declared not insane and returns home where his family greets him. But it turns out that Bart hasn't changed at all and Lisa tries to convince Marge and Homer of the fact but they don't believe her. Later that night Bart sneaks into his parents bedroom and murders them, then Lisa finds the bodies in the morning.