Second volume of the Manifold series.
Reid Malenfant inhabits the universe kick-started in the first volume, 'Time'. "If they existed, they would be here" - this is the Fermi paradox concerning the existence of extraterrestrials. Once it confirmed Malenfant's opinion that humanity was alone in the universe.
But when Nemoto, a Japanese researcher on the Moon, discovers evidence of extraterrestrial intelligence in the solar system, the same paradox provokes both Malenfant and Nemoto to question, why now? Because, suddenly, there are signs of intelligent life in deep space in all directions. Deeper layers of Fermi's paradox unravel as robot-like aliens, the Gaijin, seem to be e-mailing themselves from star to star, and wherever telescopes point, far away, other alien races are destroying worlds.
Malenfant sets out alone in a salvaged antique spacecraft to make contact with Gaijin. In response the Gaijin come to Earth and trawl through archives of human culture for their own mysterious reasons. In their wake, recreated marvels of prehistoric life once more roam the Earth, including those hominids driven to extinction by man. But the Gaijin have more questions than answers. As other aliens approach in a blaze of destruction there is no comfort in recalling Nemoto's certainty that this has all happened before, over and over. But in the soul of Malenfant, in the dreams of the new neanderthals, and in Nemoto's obsessive loathing of all aliens there are glimmers of hope that the cycle can be broken.