Jiyoung sits in front of the same bus stop at the same hour every night; Hyunmin, who takes the last bus after work and gets off at the same stop, notices her; one rainy night, he musters up the courage to talk to her and offers her his umbrella.
Sunhae rents a supposedly quiet place in the middle of an alley, but the old place is riddled with problems like leaks and flickering lights. On top of that, she hears someone singing loudly every night outside.
Detective Sungsik probes an old man's death deemed natural but appears suspicious. Unable to close the case officially, he pursues a personal investigation to uncover clues revealing the truth behind the seeming natural demise.
An undertaker in the basement mortuary on the fourth basement floor and a nurse in the eighth-floor ICU begin their night shifts at a university hospital, unaware of what awaits them. As they work, mysterious situations unfold.
