Commander Shon Ó Conaill left to find habitable planets on Canopus, one of two black-hole lightships to launch in the twenty-sixth century. Finding none, he ordered Gristelda, the ship's computer, "to accelerate us until the Canopus has achieved the maximum she will do." Gristelda complied and he found himself returning to Earth, now called Vitas, 800, 000 years in the future. Humankind is now governed by the Society of Life, charged with maintaining the Order, in world inhabited by twenty million humans and the Society. Separated from a primordial world by a Wall, after propounding a Slippery Slope Proposition, Shon is forced to cross over. But he is part of a greater plan set in motion by the Great One. What he does next will profoundly change the future of humankind, the Society, and all the intelligent habitants of the galaxy.