The Rubicon Protocol

"December 2559. Humanity has its back against the wall after the United Nations Space Command flagship Infinity drops out of slipspace into a devastating ambush launched by the Banished. As this fierce enemy alliance seeks to claim a mysterious object hidden within the ancient Forerunner construct known as Zeta Halo, the surviving UNSC corps finds itself compromised and its leadership out of reach-with remaining personnel forced to abandon ship a...