The cold war smoldering between the Realm and the Empire drags on.

Both sides now turn to the distant spinward stars for a way to break the deadlock. Cryptic signals from deep space hint at powerful civilizations, and potential allies to turn the tide in favor of one side or the other, propelling it to victory.

But who—or what—are these mysterious powers?

Lawson Sawyer and his most trusted companions lead a powerful task force to find out. With the Ravennox nipping at their heels, they launch themselves into the spinward wilds. There, they come face-to-face with humanity's distant past—and hard truths about humankind's ancient benefactors, the enigmatic aliens known as the Unseen.

Meanwhile, Darius Spann leads his own expedition on a voyage of spinward exploration. Following an intriguing trail of mystifying signals, Spann discovers truths of his own, and through them, opportunity.

The absolute power he craves will be his—if he's prepared to pay the price.

Soon, the two expeditions converge. Conflict looms, imminent and inevitable. But as the opposing factions prepare for war, loyalties are put to the test. Treachery and betrayal follow. Battles rage amid the crumbling ruins of civilizations older than humankind itself. Sawyer and Spann square off in their respective mechs, bound for a final, cataclysmic showdown. The fates of countless millions, human and alien alike, hang in the balance.

One will triumph, and return to human space. The other will be lost, vanishing into the spinward unknown.