"The Mystery of the Hidden House" is an exciting installment in Enid Blyton's beloved Five Find-Outers series. The story revolves around the clever and adventurous group of young detectives—Pip, Bets, Larry, Daisy, and their friend Fatty—as they stumble upon a case filled with mistaken identities, fake mysteries, and thrilling discoveries. When the children mistake Ernest "Ern" Goon, the village policeman's nephew, for their friend Fatty, they unknowingly set off a chain of events that lead to an unexpected adventure. With a fake mystery about kidnappers and robbers on Christmas Hill, the children hope to outsmart Mr. Goon and provide Ern with a harmless scare. However, their plans take an unexpected turn when Ern finds himself in a real and dangerous situation at Harry's Folly. Now, it's up to Fatty and the rest of the Find-Outers to solve the mystery, rescue Ern, and capture the culprits.