In book seven, the Secret Seven have a fantastic new hiding place, but somebody else has been using it too. Whoever it is is going there at night, and the gang are determined to catch the cheeky intruder, whatever it takes...Solve the mystery!

Cover and inside illustrations are by the brilliant Tony Ross, illustrator of David Walliams's books. The story was first published in 1951. This edition features the classic text and comes with a Bonus Blyton section at the back with quizzes, puzzles and other bonus extras!