Sheltered since early childhood, 17-year-old Katie Price (THORNE), lives with a rare life-threatening disease that makes even the smallest amount of sunlight deadly. During the day she is housebound, having only her father, Jack (RIGGLE) for company. But it is after nightfall that Katie's world opens up, in the dark, when she ventures out to the local train station to play her guitar for travelers. One night, fate intervenes when she meets Charlie (SCHWARZENEGGER), an ex-high school all-star athlete, whom she has secretly admired for years. She hides her condition from him as the two embark on a uniquely powerful romance that will change them – and those around them – forever.