In the year 2274, the remnants of human civilization live in a sealed domed city, a utopia run by a computer that takes care of all aspects of their life, including reproduction. The citizens live a hedonistic life but, to maintain the city, everyone must undergo the ritual of "Carrousel" when they reach the age of 30. There, they are vaporized and ostensibly "renewed". To track this, they are implanted at birth with a "life-clock" crystal in the palm of their hand that changes color as they approach their "Last Day." Most residents accept this promise of rebirth, but those who do not are known as "Runners" and "Sandmen" are assigned to pursue and terminate them.