The artifact is a huge circular ribbon of matter, some 180 million miles across, using a sun at its center. Pierson’s puppeteers-strange, three-legged, two-headed aliens-discovered this “Ringworld” inside a hitherto unexplored area of the galaxy. Curious about the immense framework, but frightened by the chance of meeting the contractors, they set about assembling a team to explore it:

Louis Wu, human-old and uninterested in having lived too fully for too many years, seeking an adventure, and all too capable of handling it.

Nessus, puppeteer-a trembling coward from a types with an inbuilt success pattern of non-violence. This specific puppeteer, however, is normally insane.

Speaker-to-Animals, kzin-large, orange-furred, and carnivorous. The kzin are perhaps one of the most savage life-forms known.

The party’s expedition, however, goes disastrously wrong when their deliver crash-lands and its own motley staff faces a daunting trek across a large number of miles of Ringworld territory.