Catching an ordinary butterfly is not a difficult task, especially if you have stun guns and automatic traps at your disposal. But catching the Papilio galaktikos, or milkworm—an intelligent psychophage that takes the form of a butterfly only during a short transition from the victim's body to its native n-dimensional space—requires very special methods. And the esthete entomologist Bugoy chooses the hot planet Pirenu as the place to hunt for the milky, the indigenous inhabitants of which have advanced further along the path of developing extrasensory abilities than all other inhabitants of the Galaxy...