Set in an unnamed Asian city, the story follows a group of commuters on the last subway train home; only to have the train veer off-course and crash into an abandoned tunnel. The tunnel seems to be a lair of an unknown monster. Our lead, a distant young mother, reflects on a past mishap resolving to bring up her son on her own. Her maternal spirit is tested in this crisis. Back in the subway control headquarters, duty engineers try to make sense of the situation and rescue the survivors, if there are any.