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.

Other titles in the series:

The Castle of Adventure

The Valley of Adventure

The Sea of Adventure

The Mountain of Adventure

The Ship of Adventure

The Circus of Adventure

The River or Adventure