The Core is the seat of empire for the Third Imperium, a highly populated and industrialized region of space civilized for thousands of years. It is also home to several reserve worlds, some of which are places where the Imperial feudal nobility go to rest and play. Tinea-Fabre is a candidate to become the fourth reserve world in the sector, hosting a lush ecosphere with dozens of imported alien animals. The Travellers are hired by the ducal heir of Alekvadin to fly a safari ship first to Akussanja, to obtain specimens of a rare and wild species, and then to Tinea-Fabre where the animal is to be deposited into a wildlife preserve. After it has settled in, the young duke-to-be enlists the Travellers to hunt the elusive creature in its adopted habitat but it proves to be a wily prey with heretofore unknown abilities. The hunters become the hunted and are seemingly forced to fight off the entire animal kingdom of the preserve. They will end up in a pitched battle for their very survival.

Invasive Species includes: A complete adventure set in the Core. The Superb Starling, a customized Type-K safari ship. New and exciting animal encounters, including the sly and ferocious shakuurzarpi of Akussanja. Maps of two wild alien worlds.