On a rainy day, several giant spiders appear in Billy and Mandy's school and start kidnapping the children one by one. Grim presumes this is somehow related to his past, but doesn't figure it out until he receives a message saying that Velma, the Spider Queen, an old friend from high school, is responsible for it. Meanwhile, Billy meets with his "son", Jeff the Spider, who informs him that he is precisely marrying Velma. After trying to recover a talking carton of chocolate milk from Jeff, Billy and Jeff get into a fight, and Jeff looks angrier than ever before. Upon meeting in the school's football field, Velma tells Grim that she has finally come to devour his skull and absorb his powers, since one hundred thousand years ago Grim cheated and robbed her from the possibility of becoming the Reaper. Converting the school into her own palace, and with help from the Dark Elves, Velma captures Mandy, Mindy, and Grim, and proceeds to devour the latter's skull. However, when Velma cracks open Grim's skull, his thoughts start coming out, and she is able to see his memories. In the following, Grim's skull is connected to a screen, and the story on how he became the Reaper is shown. It is revealed that an election was held in the Underworld's high school to choose the Reaper, in which students had to vote on the scariest participant. Velma was the scariest contester and she was getting most of the votes over the pathetic Grim and the Boogeyman. Then, Boogey decided to tamper with the ballots, and Grim in turn decided to help Velma, but she got the impression that Grim was the cheater and ran away. Then, in a fit of anger, Grim used the prototype scythe in a spectacular fashion to scare Boogey off. In consequence, the people that hadn't yet cast their vote, voted for Grim, who thus became the new Reaper. While the story is being told, Mandy and Mindy form a temporary alliance to fight the spiders, and also Billy reconciles with Jeff, and fights the spider-cow centaur-li