The Disappearing Staircase Mystery:The Aldens are helping restore an old estate. The house is bursting with the collections of its mysterious and eccentric former owner. As the children explore, they come across hidden rooms, secret passageways, and strange noises coming from the walls. What’s the secret of the Bugbee House? The Mystery on Blizzard Mountain: The Aldens are helping to map out a new trail on Blizzard Mountain. As they travel through the frozen wilderness, they learn that there’s treasure buried somewhere on the mountain! The children begin to search for it, but someone or something is after them. Is Blizzard Mountain haunted, or is someone after the treasure? The Mystery of the Spider's Clue: When their friend Sam gets a letter full of riddles from an eccentric millionaire, the Aldens are eager to help him crack the code. If Sam can solve the puzzle, he will inherit the millionaire’s money! But Sam isn’t the only one in town to receive a letter — and whoever solves the mystery first will win the prize!