Two men and a genetically enhanced talking dog called Scorpio, land on the planet Alvea, in pursuit of a fleeing Changeling. The Changelings spread chaos and disorder wherever they go, and are extremely hard to catch since they can transform themselves into an exact copy of any person or creature they like. The dog can recognise them by their smell, but unfortunately there are no dogs on Alvea, and due to the political situation two Earthmen and a dog going about the streets openly would cause a riot, so they have to be more circumspect.

Another book with genetically enhanced dogs! Scorpio has only been enhanced enough to speak basic English and follow spoken orders; his role is still to hunt by scent. Perhaps that's why he doesn't seem as unhappy as the enhanced dogs in other books. ( )