Every seven years, for one night, the peaceful planet Dante's Joy becomes both hell and heaven.

All who stay awake and take the Chance become what their inmost longings dictate: a beast howling with lust or depravity, or a godlike being flowering in truth and light. Thousands are transformed into monsters, and others find perfect happiness. Those who are afraid to take the Chance escape by lying drugged in the Sleep.

John Carmody, a conscienceless exile from Earth, arrogantly chooses to take the Chance.

It is too late to turn back. Shrieking in terror, he confronts the darkness....