Invaders from beyond the Periphery, the Clans have beaten the forces of the Inner Sphere repeatedly. Now the Clans are driving toward their ultimate objective Terra, cradle of humankind and hub of the ComStar communications network. Nothing the Inner Sphere has can stop them. The heir to the throne of the Draconis Combine is missing. Whole regiments of BattleMechs lie smashed like abandoned toys. Rasalhague is overrun. The Clans are sweeping toward the center of the known universe in a relentless tide. Humanity's only hope lies in the Inner Sphere's most powerful traitor.