Una nueva entrega de la mítica serie de misterios de Enid Blyton, actualizada para los lectores de hoy. Milton House, la casa abandonada del pueblo, no está tan deshabitada como parece. Qué misterio! Los cinco detectives desean descubrir qué ocurre allí y, de paso, probar los nuevos trucos de Fatty, pero bastarán los disfraces y la tinta invisible para resolver este caso? ENGLISH DESCRIPTION: Fatty is made the leader of the Five Find Outers, as he explains that he has been studying how to get out of a locked room when the key is not on his side, to write letters with invisible ink (or orange/lemon juice) and has been practising disguises. The Five have fun with Fatty's new techniques, particularly disguises. Pip disguises himself with a wig and some sticking out teeth and attracts the attention of Mr Goon, who chases him across the village. In an attempt to escape Mr Goon, Pip runs into the grounds of an empty house and climbs a tree. He is very surprised to see a fully furnished room at the top of an otherwise empty and apparently abandoned house. The Find Outers get to work to discover who owns Milton House, and why there is an apparently secret room. Who uses it and why?