Secret Seven : Mystery Of The Skull (Book 16 in The Secret Seven Series)

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.