In 1967, when 10-year-old Seth moves with his mother to an old house in a rural village deep in the Berkshires of Western Massachusetts, the last thing he expects to find is a new friend. But, Lily is waiting in Hadley Falls. She seems to be mysteriously attached to the old house and, when Seth's mother plans to re-marry and take him away, Lily devises a new game to keep them together.