It's been two years since his mother died in a terrible train crash, and Alaric's life continues to unravel. He and his father are barely on speaking terms, and Withern Rise, their Victorian mansion, is in shambles. Trapped at home during a blizzard, Alaric stumbles into a parallel world; a reality in which his mother is still alive. There's only one problem ... someone else is living his life.
Naia tries not to dwell on the horrible accident two years ago that nearly took her mother away. Now that life with her parents in Withern Rise has returned to normal, Naia thinks the worst is behind her. But during a freak snowstorm she's confronted by a stranger. Why does this boy look like her? Why does he have the same thoughts? The same memories? Who is he?
Alaric's and Naia's discovery of each other sets off an electrifying chain of events. And as their lives - and lifelines - entwine, the two teenagers uncover a truth with the power to rearrange, or even erase, their very existence.