The planet Kalgash is on the brink of chaos--but only a handful of people realize it. Kalgash knows only the perpetual light of day; for more than two millennia, some combination of its six suns has lit up the sky. But twilight is now gathering. Soon the suns will set all at once--and the terrifying splendor of Nightfall will call forth madness that signals the end of civilization.

This novel expands on the Asimov short story 'Nighfall', which was published in 1941.