Book Four of Five.
Four years of research, using the combined resources of five species of sentient beings, have brought the Commonwealth and its allies no closer to understanding how Humanity's sibling species came into existence. Who was responsible for redirecting the natural course of evolution on four living worlds? Why did they do it? And can they find the answer before the Faceless render all such questions moot? For the Faceless are back with a vengeance, and as implacable as ever.
The Commonwealth has known nothing but peace for almost four hundred years. Now, war is upon them. How do you prepare for something no one alive has ever seen?