Three teenagers with XP (a life-threatening allergy to sunlight) are a species unto themselves. As seen through the eyes of 16-year-old Allie Kim, they roam the silent streets, looking for adventure while others sleep. On a random summer night, while scaling a building like any other, the three happen to peer into an empty apartment and glimpse an older man with what looks like a dead girl. A game of cat-and-mouse ensues that escalates through the underground world of hospital confinement, off-the-grid sports and forbidden love.