Changeling, Isaac Asimov's Robot City

This pair of adventures, enhanced with a pair of essays by Asimov himself, continue the saga of Robot City, where the finest minds in science fiction enter the most futuristic landscape in robot history! A man without memory, tied by blood to a city of robots. At his side, a mysterious woman whose life and memory he saved, whose love he has won for a second time. His name is Derec; hers is Ariel. In Changeling, Derec must answer the call of a besieged city on an alien planet. His new challenge is to protect a fantastic metropolis of robots from wolf-like beings that stalk the perimeters and threaten its destruction! In Renegade, Ariel finds herself the sole human on a planet of positronic robots and an alien race of shocking intelligence. Can Derec and Ariel solve the mysteries of the robots and the aliens in time to stop an all-out-war?