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 remedial English teacher, Miss Isles, who became convinced it was the key to solving a puzzle. That a message in secret code 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. Now, out of prison after a long stretch, Steven decides to investigate the mystery that has haunted him for decades. Was Miss Isles murdered? Was she deluded? Or was she right about the code? And is it still in use today? Desperate to recover his memories and find out what really happened to Miss Isles, 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..