Scooby has a traumatic experience with demon Time Slime and is replaced by lazy Bernie Gumshire, but Vincent Van Ghoul shows what will happen to the gang if Scooby doesn't come out of retirement.
The Chest of Demons is stolen by a shadow monster, so the gang heads off to maze-like Befuddle Manor to retrieve it, but soon they have to contend with demon chest escapee Queen Morbidia.
The gang lands their plane in a town populated by werewolves; Bogel and Weerd trick Scooby and Shaggy into opening the chest of demons; pint-sized conman Flim-Flam joins the gang.