On Aurora, the first and greatest of the Spacer planets, Elijah Baley and R. Daneel Olivaw investigate yet another seemingly impossible crime - this time, a roboticide.

Someone has destroyed the positronic mind of R. Jander Panell, a humanoid twin to Daneel. His creator, the master roboticist Han Fastolfe, denies all involvement. So does Gladia Delmarre, the...