Title: The island of adventure / The castle of adventure / The valley of adventure
First published: 1989
Description: Book 1 - *The Island of Adventure*
 For Philip, Dinah, Lucy-Ann and Jack, the holiday in Cornwall is everything they'd hope for—until they begin to realize that something very sinister is taking place on the mysterious Isle of Gloom. But they're not prepared for the dangerous adventure that awaits them in the abandoned copper mines and secret tunnels beneath the sea.

Book 2 - *The Castle of Adventure*
What is the secret of the old castle on the hill, and why are the locals so afraid of it? When flashing lights are seen in a distant tower, Philip, Dinah, Lucy-Ann, and Jack decide to investigate—and discover a very sinister plot concealed within its hidden rooms and gloomy underground passages.

Book 3 - *The Valley of Adventure*
Nothing could be more exciting than a night flight on Bill’s plane! But Philip, Dinah, Lucy-Ann, and Jack soon find themselves flying straight into a truly amazing adventure. What has happened to Bill? Who are the two strange pilots, and what is the secret treasure hidden in the lonely valley where the children land?
Subjects: Juvenile fiction, Adventure