When Peter discovers an old skull hidden in his bedroom, it's time for an urgent meeting of the Secret Seven. Setting off to investigate, the friends see a gigantic hole in the grounds of a local hotel. Could there be any connection between the two strange events? The Secret Seven are determined to solve the mystery. It's time to look behind the green door of the Secret Seven's shed again. Enid Blyton's much-loved detective club are back in a superbly entertaining new adventure.