Buck and Twiki come across the survivors of a failed colony, a young widow and her son. The woman tells Buck that the other colonists all fled the planet as the result of a plague. Buck is confused by the woman's refusal to leave the planet despite being repeatedly being menaced by a goat-man named Pangor; but he soon discovers the truth about the plague when he contracts it and begins to turn into a goat-man himself.

Buck, Wilma, and Hawk explore a strange planet and come across the wreckage of a spacecraft and its lone survivor. He is taken back to the Searcher by Wilma, while Buck and Hawk continue to explore. After some unexplained happenings on the planet, they return to the Searcher, where they find that everyone has undergone personality changes -- becoming the opposite of their real selves. Buck soon learns that he can not even trust Wilma and Hawk to help him solve the mystery of what has happened.