Roger, Diana and their orphaned cousin Snubby, along with his dog Loony, go on holiday to Rockingdown with their mother's old governess Miss Pepper, but with the prospect of lessons taken by a tutor while they are there they feel sure they will be in for rather a dull time. Then they meet Barney the circus boy, who is searching for his longlost father, along with Miranda, his pet monkey, and suddenly Rockingdown isn't quite so dull after all. A mysterious old house with an abandoned nursery, noises in the night, and a tutor who is acting suspiciously, all add up to a first exciting adventure for the four children, where friendships are forged and mysteries need solving...