A young woman in South Korea lives alone in a fully smart home, surrounded by technology meant to make her life easier. But little by little, the devices begin acting strangely: lights flicker for no reason, security cameras move on their own, and even her phone seems to watch her in the silence of the night. Everything gets worse when she starts receiving messages from an unknown number.

“You look beautiful today.” “Don’t be scared.” “How was your day?”

As she tries to discover who is behind it all, she realizes someone knows every detail about her life. Behind the screens is Christopher Bang, an obsessive man who turned her home’s technology into a silent form of surveillance — and perhaps something even more dangerous.