The Alexander children are horrified that their normal holiday plans are altered when their parents are called to work, and the kids have to stay with their most feared relative—Groppy (Great Aunt Poppy). There is something strange and creepy about her house and the kids swear she is a witch. But the mood quickly changes from fear to intrigue when the siblings stumble upon Groppy’s magic cauldron and wish-granting potion. Ava, Nolan, and Charlotte Alexander create instant chaos when spells get out of hand and only Groppy can save them. They might just survive this holiday visit after all, but something chilling hides deep in the woods and not even Groppy's magic can stop it. The three siblings must use quick-wit and bravery to help Groppy capture a terrifying werewolf and, preferably, not get eaten.