After surviving a car accident that claimed the life of her best friend, Teresa is now terrified to leave the safety of her bedroom. Since then, her only solace and window to the outside world has been the online community she found through streaming.

But one night, the safe world Teresa created starts to break down. A shadowy figure appears in the background of her favorite's streamer's video, and his behavior mysteriously changes over the next few days before he dies in front of thousands of viewers. Teresa finds herself at the center of a life-and-death investigation as the world tries to figure out what or who this figure could be . . . especially as it begins appearing in the other people's streams, compelling them to "open the door" and let it in--including Teresa's own. In order to save herself and the rest of the internet from this relentless entity, Teresa must venture outside of the mental and physical walls she's created. But will she be able to conquer her fears before anyone else loses their life?