Greenglass House is a mysterious winter adventure about Milo Pine, a twelve-year-old adopted boy who expects a quiet holiday at his parents' inn. Instead, unexpected guests arrive with hidden agendas, pulling Milo into a search for a legendary smuggler's treasure. With the help of Meddy, the cook's daughter, Milo adopts a daring thief persona to solve puzzles and uncover secrets about the house and himself. The story blends cozy mystery with deep questions about identity, family, and belonging.