It's been eight years since an alien invasion drove a small surviving group of settlers to seek refuge in an underground shelter. Cut off from the rest of humanity, the ragtag band has maintained a narrowly functioning colony due to communal effort and salvage runs. Alex Archer has her own duties as a dog handler. While this off-world colony may be harsh, Ash, Alex's black shepherd raised to sense threats, makes living in it a little nicer.

But the tenuous hide-and-seek with the monstrous species known as the Lankies is about to come to an end for Alex and her close-knit crew of soldiers, techs, and friends. When a salvage operation goes catastrophically wrong, the Lankies home in on the humans.

With hopes of a rescue long faded, all Alex has left is will--and the fear that there's so much more to lose.