Ten-year-old Hope is a bit of a loner with a wonderful imagination. Growing up in the 1950s with a single mother and a mysteriously absent father, the letters she writes to her imaginary friend, Grace, help her cope with the difficult times in her life: her mother's depression, their money worries, struggles to make friends at school and her grandmother's death.
On her eleventh birthday, Hope is shocked to learn that Grace is a real person--her twin sister, who contracted polio and was adopted when they were toddlers. Hope believes that finding Grace is the only way she can help her mother deal with her guilt. Hope's hunt for her sister takes her and her mother to the tiny community of Harrison Hot Springs, British Columbia. There she finally meets Grace, who is all the things Hope wishes she could be. They become friends, but Hope doesn't know how to tell Grace the truth. How can she have a relationship with her sister based on lies and secrets? A crisis will force her mother to be the adult she needs to be and allow Hope and Grace the chance to be children together.