A British children's book author comes to Springfield to give a talk at Springfield Elementary School. Homer is tasked with picking her up from the airport, but things go bad from there.

Bart and Lisa adopt an abandoned baby chimp and clash over their surprisingly different parenting styles. When the chimp is abducted by a private wild animal zoo, the family goes on a mission to rescue him. Homer is conflicted about saving the ape, because he's convinced the chimp will tear off his face and groin.

All hell breaks loose on Halloween when a killer comes to Springfield and hacks their way through town. No Simpson is safe from... THE REVENGENING!