The Human Commonwealth of Worlds had colonized their small corner of the galaxy for almost four centuries before an intelligent non-human species was encountered. During that time hundreds of stellar systems were settled in an effort to spread life out into the Great Void, creating a thriving culture shared by flesh and blood people and machine minds known as Artificials, vast intellects that opened the way to the stars for the Human species. The economics of scarcity and want are ancient history, and illness and old age have been banished. The Commonwealth is a civilization at peace with itself, but it is all Humanity knows. Like many citizens of the Commonwealth the crew of the probeship William Bartram has come to believe Humanity is alone in the galaxy. Then they meet the Leyra'an. In that encounter they find an unsettling mystery, for the Leyra'an are so similar to Humans that it defies both science and belief. But before the crew of the probeship can investigate this mystery, there is a darker and far more dangerous matter before them. Someone else met the Leyra'an first, and started a war.