Perdita, a lonely orphan who lives in an old house on the island of Skua, has never gone to school and can neither read nor write. The island children are afraid of her because they believe her to be a witch's daughter. The housekeeper in the tumbledown house is her only support. The Hoggart family come to the island for a holiday - mum, dad, Tim and Amy, who is blind. Amy and Perdita form a friendship through their different kinds of loneliness. The children become enmeshed in an exciting mystery involving some elusive jewels, and in the tremendously exciting final chapters, Amy leads the children from a dark cave where they have been abandoned. She is able to do this because she 'sees' with her hands and feet, and darkness holds no terrors for her. The most important aspects of the book are the characters of Perdita and Amy. Amy is determined to be treated as normal and can be unpleasant in her demands to be so, but she proves her ability over and over. Perdita's loneliness and difficulty in communicating with others is painful, as is the island community's willingness to allow their children to be unkind to her. There is hope for her at the end of the story, but life will not be easy for this unusual child. A tremendously alive story.