This is the first book in the Adventure series called, The Island of Adventure.

For Philip, Dinah, Jack, and Lucy-Ann, a holiday together in Cornwell is all they hoped for... until they find out that criminals have an evil plot on the deserted Isle of Gloom. They soon find out that these are very dangerous men - and they will do anything to stop the junior investigators finding out about their plan.

I would recommend this book to people who like suspense, action, and adventure.