Haunted Castle on Hallow's Eve (Magic Tree House Merlin Mission Series #2) by Mary Pope Osborne, Sal Murdocca The #1 bestselling chapter book series of all time celebrates 25 years with new covers and a new, easy-to-use numbering system! Jack and Annie are summoned once again to the fantasy realm of Camelot. There, Merlin the Magician tells them that the Stone of Destiny has been stolen. The answer to its disappearance lies within a haunted castle. With a young magician named Teddy, Jack and Annie take on the challenge in an adventure that takes them to new heights and places they couldn't even imagine! Formerly numbered as Magic Tree House #30, the title of this book is now Magic Tree House Merlin Mission #2: Haunted Castle on Hallows Eve. Did you know that there's a Magic Tree House book for every kid? - from Amzon