A man named "M" invites seven people to a murder game party. Among the eight in the room, one will become a victim, and another the culprit.

The detectives receive a text message from K that was written three months ago. It asks them to come to Incheon, where their final test awaits.

Trapped in individual rooms filled with a variety of challenges, each detective tries to figure out how to escape.

The search for K's killer gets complicated when a series of dead bodies are found -- all with a mysterious QR code on them.