Herb returns to the remote planet he has been furtively trying to build a city on, to find it a swarming nightmare of self-replicating machinery. Eva has taken desperate steps to escape the tedium of her pointless life ... only to end up in the super-intelligent clutches of a yellow mechanical digger. Constantine arrives at the remote part-idyllic, part-nightmare settlement of Stonebreak and - unsettlingly - begins to confront the truth of his own unreality.

Meanwhile in the farthest reaches of outer space, the Enemy is plotting the final overthrow of the human race which created it.