During Spartan-IV first class's tour of the UNSC Infinity, former Spartan-IV test subject Ilsa Zane devises a plan to steal the ship with the help of an insurrectionist organization known as the New Colonial Alliance. The newly augmented Spartans are forced to put on their MJOLNIR armor and fight off the attack, successfully repelling the insurrectionists. Ilsa Zane is ejected into space, though she manages to survive the attack.
Initiation follows the crew of the UNSC Infinity, particularly the initial class of Spartan-IVs led by Sarah Palmer.
Initiation takes place on the newly completed UNSC Infinity.