Enid Blyton's much-loved classic series, packed full of adventure and mystery. Philip, Dinah, Lucy-Ann and Jack are going for a night flight on Bill's plane and soon find themselves flying into a truly amazing adventure. What has happened to Bill? Who are the two strange pilots, and what is the secret treasure hidden somewhere in the lonely valley the children have landed in? First published in 1947, this edition contains the original text and is unillustrated.