The Spider Queen wants to take revenge on Grim for denying her the rightful place as the Ripper.

An evil sorceress transports the gang back to the age of chivalrous knights, spell-casting wizards, and fire-breathing dragons.

Irwin, Hoss Delgado, Jeff the Spider, Fred Fredburger, and General Skarr from the "Grim Adventures of Billy and Mandy" team up to fight an evil candy army from the Underworld on Halloween.