When her parents go away for a month-long business trip, Arlie Metcalfe and her little brother, Michael, get to stay with their fun-loving aunt, Isabel.It seems as if it's going to be a month-long vacation, particularly for Arlie, who's looking forward to the time away from her demanding mother.But only a few days into the trip, Arlie's parents are seriously injured in a car accident, and her mother falls into a coma. On the very same day, a new girl arrives in Arlie's fifth-grade class.Casey has the same short brown hair, the same stubbornness, and the same bossiness as Arlie's mother.Is it possible that she is actually Arlie's mother as an eleven-year-old girl? Can Arlie somehow help her mother by befriending Casey? Or is this a gift from the universe for Arlie: a strange and wonderful way to know her mother before she was her mother?