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.