Humanity has spread across the galaxy and, after years of interspecies warfare, entered into an uneasy truce with the Krell. But when the Krell send an ambassador to the human Alliance to request aid, they discover that their civilizations face a much deadlier mutual enemy: the Shard, an alien super species that are pouring from the Outer Dark into real-space.
Captain Keira Jenkins of the Alliance leads a team of simulant soldiers in a joint military action, but when the mission goes down in flames, an injured and humiliated Jenkins is offered one last chance at redemption: a mission deep into contagion-infested enemy territory.
She has one last chance, and so does mankind.