Forty years ago, Steven “Smithy” Smith found a copy of a famous children’s book by disgraced author Edith Twyford, its margins full of strange markings and annotations. When he showed it to his remedial English teacher Miss Iles, she believed that it was part of a secret code that ran through all of Twyford’s novels. And when she later disappeared on a class field trip, Smithy becomes convinced that she had been right. Now, out of prison after a long stretch, Smithy decides to investigate the mystery that has haunted him for decades. In a series of voice recordings on an old iPhone, Smithy alternates between visiting the people of his childhood and looking back on the events that later landed him in prison. But it soon becomes clear that Edith Twyford wasn’t just a writer of forgotten children’s stories. The Twyford Code holds a great secret, and Smithy may just have the key.