Forty years ago Steven Smith found a copy of a famous children's book its margins full of strange markings and annotations. He took it to his English teacher Miss Isles who became convinced it was the key to solving a secret code that ran through all Edith Twyford's novels. Then Miss Isles disappeared on a class field trip and Steven's memory won't allow him to remember what happened. Desperate to recover his memories and find out what really happened Steven revisits the people and places of his childhood. But it soon becomes clear that Edith Twyford wasn't just a writer of forgotten children's stories. The Twyford Code has great power and he isn't the only one trying to solve it. . .