Dr. Shona Taylor, a specialist in environmental medicine, uses her training and a most unusual menagerie of animal assistants to solve medical mysteries. She has an Abyssinian cat who can detect environmental hazards, a dog whose system can synthesize vaccines, and an alien ottle named Chirwl. On Chirwl’s planet, visiting humans and the local population are both suffering from a mysterious epidemic of rapid aging. Shona has to discover not only a cure, but the source, before the entire colony dies of old age.