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.

John pushes Silver Team to its limit as he searches for missing Spartans; Kai worries about John's stability; Kwan finds the Rubble is a far more dangerous place in Soren's absence; Halsey seeks the identity of her captor.

John and Silver Team embark on an unsanctioned mission; Laera, Kwan and Kessler must escape Soren's mutinous crew; Ackerson receives troubling intelligence from Cortana; the threat of an attack forces Ackerson to make an irrevocable decision.

A Covenant assault threatens humanity's most important stronghold; John, Perez and Silver Team fight an overwhelming enemy; Adm. Keyes rallies the UNSC forces to make a stand; Halsey and Soren must work together to escape captivity.

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.