Walls within walls

For sixteen years Rolf's parents had kept him hidden away from the society in which they lived. His twin brother was able to move about freely and indeed was regarded by all as a young man of talent and great promise. But Rolf was a mutant and, as such, illegally alive. What happens when he escapes from his hiding place and discovers a whole world of mutants living underground, beneath the highly controlled technologically advanced city that had been his prison.