Merlin's Cove is the perfect place for a holiday. Its golden sands, towering cliffs and mysterious caves promise three weeks of fun for Roger, Diana, Snubby and Barney.

But is all as it seems? On Snubby's first day on the beach, he is frightened by a bearded stranger. What does the man want, and who is his friend, the sinister birdwatcher?

The four friends decide to find the answers - and their holiday turns out to be more exciting than they could possibly have imagined...