How do we define being human?
Human colonists on a bequeathed new world struggle as they learn techniques to adapt, but a restive faction of purists question the cost.
Since the Year of Arrival, people from Earth and eight indigenous people from tau Ceti Epsilon minor work together to establish a home on an alien world they rename Mir. As the settlers manipulate their genes to adjust to their new environment, disquiet grows. Genethicist Stella Singh wants a normal, comfortable life for her family, but when purists question survival as unaltered humans or not at all, she takes a stand. The remaining Ceticians will soon become extinct, a possibility for humans, too, if they can't cooperate and learn how to live on eccentric Mir.
Meanwhile, a left-behind colonist on Earth's moon is strong-armed by rebels to lead the way through a dysfunctional travel stream to the place he never planned to go-Mir. An accident in time sends him searching through time to find and warn his friends of treachery to come.
Mysteries left underground and unrest threaten to unravel the delicate balance of civilization on Mir. A chance to return to Earth forces the colonists to rise and face their humanity or watch it fall forever.