[The Shadow Cage and Other Tales of the Supernatural] is not a collection of ghost stories intended to appeal to children of a certain age who, as is well known, like spooky stories. It isn't a way of keeping children quiet for an hour, or a way of persuading them to exercise new-found skills in reading. It isn't designed to make them more understanding, more sensitive or more aware of the world around them. It is not, in short, an educational device. It is literature.
Most children must know the feeling that some places and things are frightening for no obvious reason. Philippa Pearce knows about them: the dark place at the back of the cupboard, the space behind the window of the empty house, the inexplicable nastiness of the old biscuit barrel. She expresses this sense of mystery and menace without in any way explaining it away.
Dorothy Nimmo, "Seven to Eleven: 'The Shadow Cage and Other Tales of the Supernatural'," in The School Librarian, Vol. 25, No. 3, September, 1977, p. 245.