Katie, a 17-year-old, has been sheltered since childhood and confined to her house during the day by a rare disease that makes even the smallest amount of sunlight deadly. Fate intervenes when she meets Charlie and they embark on a summer romance.

Set amidst a wave of violent animal attacks sweeping across the planet, a young renegade scientist is thrust into a race to unlock the mystery behind this pandemic before time runs out for animals and humans alike.