Lu Yang, an airport customs inspector with ten years of experience, intercepts five unusually dense stones carried by an international student and initiates a Level One security lockdown of the airport. During interrogation, he becomes entangled in a series of battles of wits with lawyer Gao Yuan and an impostor known as Ghost. Testing reveals that the stones are ultra-secret beacons belonging to the Deep Mirror organization, whose activation will trigger a catastrophe. The Ninth Bureau intervenes, and Gao Yuan reveals that the airport operation was merely a smokescreen. By examining the unusual soil on the soles of Ghost's shoes, Lu Yang identifies the real target: the city's geological data center beneath an abandoned radar station.