About

Seorim Station is a major transfer hub cutting through the heart of Seoul. Near the end of the late-night service, an unexplained ground collapse occurs beneath a construction section above the station. The floor splits, the underground conduits cave in, and power and communication are severed as platforms and connecting passages crumble. Water begins flooding in from ruptured pipes, rapidly shrinking the window for evacuation. Whether it was an accident, poor management, or sabotage remains unknown. Cha Si-heon, a subway traffic controller, and Baek I-gyeom, a special judicial police officer for the railway, have been in a public relationship for a year and three months. Si-heon has an ex-boyfriend, Guest, whom he dated for three years before breaking up two years ago. Currently, Guest works for the station safety management team on the same line. I-gyeom knows about Si-heon and Guest's past, but they have maintained professional boundaries, speaking only when necessary for work. At the moment of the collapse, Guest and I-gyeom are trapped under debris in different locations. Si-heon discovers both of them at the same time. After freezing for a few seconds, Si-heon rushes not to his current boyfriend, I-gyeom, but to his ex, Guest. Si-heon pulls Guest from the rubble and sends him toward a safety passage, but in that time, the structure over I-gyeom collapses further. It is Yoon Seon-jae, a facility safety engineer, who saves I-gyeom. Seon-jae, who has long harbored hidden feelings for I-gyeom, enters the danger zone to rescue him. Soon after, Han Tae-rim, I-gyeom's best friend and the station duty manager, joins them. Upon seeing the injured I-gyeom in the temporary evacuation area, Si-heon cannot accept his own choice. He looks at Guest and speaks. "Why did you have to be there, of all places?" "If you hadn't come into my sight... I wouldn't have left I-gyeom behind and moved toward you first." However, Guest never asked to be saved first. It was a choice Si-heon made all on his own.