Lance Corporal Hondo McKeever is a peacetime Marine. Humanity is involved in a limited war with the alien Klethos, where gladitorial combat decides the fate of worlds, but that doesn’t affect the common Marine or sailor. His career has been training hard but never seeing actual combat. All of that changes when a new enemy invades the galaxy, one that threatens both humanity and Klethos. Mankind hasn’t fought an all-out war in centuries, but they’re about to. McKeever is assigned to a special task force with the mission to find out what makes this new enemy tick, and, if possible, stop them in their tracks before humanity is eliminated like so much insignificant vermin.

Marine Sergeant Hondo McKeever, a veteran of fighting the Grubs, is training his new squad to become part of the Human-Klethos alliance aligned against the deadly enemy. When the Brotherhood-led alliance tries to disrupt the war effort, however, fighting breaks out between the human forces—when they can least afford it. Federation Assistant Vice-Minister Skylar Ybarra, humanity’s foremost expert on the Klethos, uncovers a vital fact, one that could turn their Klethos allies into deadly enemies, bent on humanity’s destruction. Humanity is at a crossroads—with the almost invincible Grubs on their relentless and inexorable march into human space, war has broken out between the Brotherhood and Federation-led alliances—all while the Klethos are preparing to revert to being the mortal enemy of man. What can a Marine sergeant and a mid-level bureaucrat do to avert the total genocide of humankind?

Humans and Klethos have reforged their alliance to push back the Grub invaders. Their combined military forces seem to be holding their own through new technology and tactics, but the alliance isn’t the only side making adjustments. The Grubs develop their own new advantage, one that will make them almost unstoppable. Staff Sergeant Hondo McKeever and Ben, his Klethos Interrecon partner, are tasked with ferreting out the Grubs’ new secret technology. Even if they are able to snatch a sample, will Vice-Minister Skylar Ybarra be able to lead her R&D team to not only make sense of it, but also to develop a countermeasure before the Grubs overrun the galaxy?