When Leo Connell finds out that her younger sister and lifetime best friend, Gemma, has leukemia, her whole world turns upside down. When doctors suggest that their family should move to Minnesota to get better care for Gemma, they agree without a second thought. Leo doesn't care where she is as long as Gemma is okay. But Gemma is worse than they thought, and Leo soon learns that she doesn't have much time left. Seeking only comfort, Leo joins a support group at a church near the hospital. What she finds, though, is greater than anything she has ever known.