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 sons 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 a madness that signals the end of civilization.

Can the believers of legend pull their planet through the crisis?