Griffin Campbell is a 12-year-old boy whose world is turned upside down after his father moves his family from Chicago to the town of Sulphur Springs, Louisiana to take ownership of an abandoned hotel known as The Tremont.

After hearing that the hotel might be haunted by the ghost of a girl who disappeared decades ago, Griffin and his best friend set out to solve the mystery of what happened to her. This leads them to a portal that lets them travel back in time, where they learn that the secret to solving the mystery is meeting Griffin's own father.