The Mystery Series: The Mystery of the Secret Room: Book 3 Enid Blyton

Pip discovers a room in Miss Crump’s old empty house isn’t empty at all – someone has been using it! It’s the perfect mystery for Fatty to put his new talent for disguises to use. Now it’s up to Fatty and Pip along with Bets, Larry, Daisy and Buster the dog to find out who has been using Miss Crump’s old house.