Winnie Schulde can see splits: the moment when two possible outcomes diverge, one in her universe and one in another. She keeps it a secret; she knows the uses to which it might be put in the midst of a raging WWII. Her physicist father, made cruel by his grief after the loss of Winnie's mother, believes that if he pushes her hard enough, she can choose one split over another and maybe, just maybe, change their future and their past. When his experiment goes wrong, his lab assistant Scott is seriously injured. Winnie chooses the split where Scott is unharmed-- and is pulled into another universe. One that already has a Winnie.