The Legend of Pumpkin Guts.
Curious to know the secret behind Halloween, Mavis and her cousins break out of lockdown to find the truth before Aunt Lydia discovers them missing. At the Vampire Council, Dracula runs off to find and protect Mavis. He reveals to her that many centuries ago, a curious young monster had caused the mythical "Pumpkin Guts" to rise and terrorize the monster world and that he was the culprit. He and Mavis then fight as bats to stop it and learn that candy is its weakness.