The little town of Castle Rock, Maine, has witnessed some strange events and unusual visitors over the years, but there is one story that has never been told - until now. In the summer of 1974, twelve-year-old Gwendy Peterson encounters a stranger sitting on a park bench, dressed in black jeans, a black coat, and a black bowler hat - unusual for such a warm day. This man in black is here in Castle Rock specifically to pass along an obligation for Gwendy that is both fantastic and terrifying: on his behalf and for an unspecified period of time, she must take possession of and hide from the rest of the world a small mahogany box adorned with multicolored buttons and levers. The reward for safeguarding the box will transform her life in ways Gwendy could never imagine, but the price to pay for her failure could very well mean the end of everything...