50,000 years ago, the planet Garth was leased to the Bururalli who nearly destroyed its ecosystem by overhunting all large indigenous species. The ecologically sensitive galactic civilization killed all Bururalli, demoted their patrons, the Nahalli, to clients of the Thennanin, and began working to preserve and repair the remaining ecosphere of Garth. Several decades before the start of the novel, Earthclan acquires the lease on Garth in return for their expert assistance in biosphere recovery. The Z'Tang complete a final ecological survey before the planet is passed on to EarthClan.