In book three, the Secret Seven have a new meeting place - a treehouse! But someone else is using it too. The gang are furious, but then they learn the intruder is in big trouble and needs their help. Can the Seven come to the rescue?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!