You watched her die. And her death has created a vacancy. When Emily lets a stranger step out in front of her, she never imagines that split second will change her life. But after Emily watches a car plough into the young mother - killing her instantly - she finds herself unable to move on. And then she makes a decision she can never take back. Because Rose had everything Emily had ever dreamed of. A beautiful, loving family, a great job and a stunning home. And now Rose's husband misses his wife, and their son needs a mother. Why couldn't Emily fill that space? But as Emily is about to discover, no one's life is perfect ... and not everything is as it seems.