Derec has been infected by chemfets by Dr. Avery, and Ariel is recovering from her bout with Amnemonic plague. Mandelbrot and Wolruf are with them as they use a Key of Perihelion to go back to Robot City so that they can find Avery and make him cure Derec.

Dr. Avery is a genius architect roboticist from Aurora, who sent robots to an uninhabited planet to build a city. Derec and Ariel briefly met him after they had put on a performance of Hamlet. Dr. Avery didn't prove to be very congenial, first knocking out Mandelbrot, and then restraining the humans. Derec and Ariel managed to escape from captivity and from the planet using Avery's spaceship. (See book 4). After some adventures on Earth (book 5), they are now back on Robot City.

The whole premise of the book is that they are going to sneak up on Dr. Avery and force him to remove the chemfets from Derec. I know they are trying to sneak up on Avery, because the whole book they are being chased by Avery's robots, who if they catch Derec & Co. will undoubtedly take them to Avery.

Do not read the introduction by Isaac Asimov, half way down the first page he gives away the ending of this book.


The main characters kept telling us the current danger. I found that a bit too much, maybe there could have been some direct observation rather than this just being the characters thinking out loud. I think these books, the series not just this one, are directed at a younger audience, but this one seemed more so.