And beneath this ruined world, Dr. Catherine Halsey has discovered an ancient secret…one that could alter the course of the war. Meanwhile, the Master Chief and Cortana lead a second group toward a gathering of Covenant warships, as the United Nations Space Command’s worst nightmare has finally come true: the Covenant has discovered the location of Earth and is forming a massive fleet to utterly destroy it, as well as all who oppose the indomitable will of the Prophets…