Earth will never be the same. As the Covenant move ever so closer to achieving their goal, Earth, they must first deal with the loss of Halo, and the growing heretical movement led by Sesa 'Refumee. Thel 'Vadam is brought before the High Council for his crimes, and is instead transformed into the legendary Arbiter and ordered to hunt down Sesa and his followers on a mining facility on the gas giant Threshold. As the battle for Earth escalates, John will be thrust battle into the clutches of the Flood, and will discover yet another ring world . . . Delta Halo.