A provincial Russian town is ravaged by a wave of inexplicable teen suicides. Rebellious and sharp-witted schoolgirl Dana grieves for her younger sister, a once-happy kid who suddenly withdrew and stepped in front of a train. Desperate to learn what happened, Dana explores her sister’s online history, discovering a sinister social-media game that encourages youths to take an escalating series of self-harm challenges – 50 tasks in 50 days. Beginning with actions designed to alienate them from friends and family, the challenge breaks its victims lives apart to push them past any point of return. Hungry for answers and out for revenge, Dana registers for the game, opening a doorway into the cruelest of hidden online worlds. One that will jeopardize the lives of everyone she cares about.