Enid Blyton 
Adventurous Four Again 

Tom, Jill, Mary, and their best friend, fisherboy Andy, are off on another smashing holiday trip in Andy’s boat – a trip along the rugged Scottish coast to a lonely cliff where they can watch birds and camp for a night. However, things at the lonely cliff are not as they seem, and the mysterious happenings soon throw the four into another thrilling adventure…