In the 23rd century, a domed city houses survivors of war, overpopulation, and pollution, governed by an AI that controls every aspect of their lives. Babies are produced by the computer, and no parents raise them. People wear gems on their hands that change color as they age, with red indicating imminent termination at age thirty known as "Carousel". Rebels known as "runners" try to escape this fate, pursued by the "sandmen" police. Logan 5, a sandman, encounters intrigue as he attends a Carousel event.