Overpopulation and new, uncontrolled strains of disease -- both by-products of the medical science of the 1900's -- have become the major problems of this eastern megalopolis in the first quarter of the next century. A National Health Control enforces rigid eugenics laws, and it is illegal for doctors to treat people who have not had themselves sterilized, but many rebel, and an intricate, underground medical black market develops. Against this background of routine transplants, programmed robot surgery and systematic electronic eavesdropping, Alan Nourse weaves the tense, rapid-paced subterfuges of Doc, an old-time idealist, and his medical supplier, or ""bladerunner,"" Billy Gimp -- who cope with an epidemic and thus prove their indispensability when the National Health breaks down. It all turns out better than it has any right to, but Nourse skimps neither on physical confrontation nor on his detailed scenario of technological nightmare.