Anna is a kind and generous girl who was conceived to help her sister Kate, who has leukemia, live by donating her bone marrow. Kate has been battling cancer since age 3 but her mother Sara refuses to let her die. As Kate grows up she understands she will eventually die, so she creates a scrapbook of memories for her family. Sara is obsessed with saving Kate and does everything for her, even allowing Anna to be conceived, while Kate's father Brian tries to convince Sara that Kate will die no matter what.