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?