The galaxy is reeling. Humanity is expanding. And the enemy isn't finished with us yet. In the aftermath of Poseidon II's devastation, humanity pushes forward, determined to expand despite the Thephari threat. As colony worlds like Xanadu, Gilead, and Nubium rapidly develop, the Space Defense Force struggles to provide adequate protection across an ever-widening frontier. The fight for tomorrow is far from over. Orbital Ranger Erik Canyon and MOCOM pilot Titus Briggs are veterans who've survived the worst the galaxy can throw at them. But when an SDF Intelligence agent reappears with an unusual request, their already complicated lives take an unexpected turn. Instead of combat, Canyon is tasked with leading security for a diplomatic mission to Kylos Major, home to a mysterious third alien species that could tip the balance of power in humanity's favor—or become its next existential threat. Meanwhile, Briggs finds himself caught between loyalty to the SDF and lucrative opportunities with Talos Armament Solutions, where former teammates have already jumped ship. With each new battle, the divide between Canyon and Briggs grows. In this thrilling fifth installment of the bestselling series, Anspach and Chaney deliver their most intense battlefield action yet, as humanity's expansion becomes a desperate race against an enemy that strikes without warning, leaving our heroes to fight not just for their lives, but for the soul of human expansion itself.