Six-year-old Gracie Lynn is perpetually curious and bighearted. Convinced she knows how to save her beloved grandfather John from the ''worm'' that is eating his brain - a metaphor her mother once used to explain John''s dementia and sundown syndrome - Gracie helps him break out of his nursing home, and the two disappear together on a quest to chase the sun. But what''s an adventure for Gracie is a nightmare scenario for her estranged parents, LeeAnn and Dan. There''s no way to predict where John might have taken their young daughter, or if he''s capable of keeping her safe.