The Greens prepare for their Halloween party, and Tilly feels bad for Bill, who's disappointed by the poor yield of his small pumpkin patch. When they visit BigTech to make a produce delivery, Tilly secretly "borrows" Gwendolyn Zapp's alien chemical compound to make Bill's pumpkins grow bigger. At first, it works, making the pumpkins larger, but it also mutates them into bodysnatching alien monsters.