A deadly evacuation mission signals a shift in Master Chief's war with the Covenant. On Reach, a new regime takes the reins at FLEETCOM. John senses a looming threat close to home.

In the aftermath of defeat, the survivors struggle to pick up the pieces. On the desolate planet of Aleria, John grapples with an unprecedented loss. Soren and Laera search for their missing son. Makee treads carefully as the Arbiter grows impatient.

John seeks revenge on a secret ONI planet. Perez trains to become a new kind of soldier. Kai finds herself torn between her Spartan code and her loyalty to Master Chief. Makee turns to Cortana for help in her search for the Halo.

The climactic battle for the Halo begins. John makes a fateful choice. Soren and Kwan undertake a rescue mission. Halsey and Miranda unleash an ancient horror.