In their magic treehouse, Jack and Annie are again transported to King Arthur's realm, where invisible beings, giant ravens, and mistaken magic spells have a duke's castle in an uproar on Halloween night.
Hired to cater a charity haunted house at the old Peabody School, sisters Bernadette and Libby Simmons find murder on the menu when the death of wealthy socialite Amethyst Applegate could hold the key to solving the decades-old "accidental" death of a young girl.
When nine-year-old Alex and his friend Yasmeen investigate the disappearance of cats in their neighborhood, they stumble onto a larger mystery involving a haunted house and a ghostly cat.
Nikki's diary describes a frightful Halloween, on which she helps with her sister's ballet class party at the same time she is Brandon's date for their middle school Halloween dance, where she has promised to spend the evening with her two best friends.