This is the fifth and last novel in Larry Niven's "Ringworld" series. This series began in 1970, with the publication of Ringworld, now, in conjunction with Edward M. Lerner, Niven brings the series to its conclusion.

For decades, the spacefaring species of Known Space have battled over the largest artifact—and grandest prize—in the galaxy: the all-but-limitless resources and technology of the Ringworld, but without warning the Ringworld has vanished, leaving behind three rival war fleets. Something must justify the blood and treasure that have been spent. If the fallen civilization of the Ringworld can no longer be despoiled of its secrets, the nearby advanced, but pacifistic species known as "Puppeteers" will be forced to surrender theirs. Yet, the danger to the Puppeteers goes far beyond mere invasion fleets, the survival of their planet is at stake, plus political intrigue, deadly rivalries, risk and danger at every turn.