Vanessa stumbles upon something unexpected in an apartment hundreds of floors above the ground: a dead body next to a single beeping monitor. In another part of the city, Criselda mulls preemptive violence after her Mod shuts down to show her a boy, a bird, a window. Is her Mod malfunctioning, or is she being manipulated? Set in a city of towers, where residents undergo biomodification in order to work more hours and earn more money, where living in the Upper Floors is the ultimate dream, Nightfall unfolds in a series of interconnected stories, exploring the lives of characters whose fates intersect and intertwine, revealing the paths they have taken to bring them to this dark night.