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. Season premiere.

John goes rogue with Silver Team. Laera, Kwan and Kessler attempt escape from mutineers. Cortana gives Ackerson alarming intel. Looming attack forces Ackerson's fateful choice.

As the Covenant start their assault on Reach, John and Perez fight to join up with Fleetcom. Halsey and Soren form an unlikely alliance.

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.

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.

John-117 comes face to face with Makee. A revelation leads Ackerson to question his loyalties. Soren and Laera's relationship begins to fracture. Halsey, Kwan and Miranda work to solve a mystery.

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.