December 2553. Less than a year after the end of the Covenant War, a string of violent incidents continues to threaten the tenuous peace in human-held space ... culminating in the assassination of UNSC fleet admiral Graselyn Tuwa and the abduction of her family. It is a provocation so outrageous that the Office of Naval Intelligence must retaliate swiftly and ferociously-but only after its operatives identify her killer and rescue the hostages.

This mission will be the first for homicide-detective-turned-ONIoperative Veta Lopis and her young team of Spartan-IIIs, and something feels wrong from the start. The obvious suspect is an infamous Brute who leads the Keepers of the One Freedom, an ex-Covenant splinter group in fierce opposition to the UNSC. But Lopis and her team soon realize that the truth is much more insidious than they could ever have imagined, and with Fred-104, Kelly-087, and Linda-058 of Blue Team for combat support, they must stop a plan hatched in the bowels of the secret research station Argent Moon-a plan so sinister it could destroy all those still reeling from thirty years of intergalactic conflict ...