Griffin Campbell, a 12-year-old, relocates with his family to the quaint town of Sulphur Springs, where they acquire an old hotel said to be haunted by the spirit of a girl who vanished many years prior. Griffin forms a friendship with Harper, a curious and mystery-loving classmate. Together, they discover a hidden portal that enables them to journey into the past. There, they strive to unravel the mystery surrounding the girl’s disappearance, a puzzle that has implications for everyone around them.