As usual, of course, the fate of the universe rests on Master Chief's long-dormant shoulders -- the green-armored super-soldier has been on ice aboard the Forward Unto Dawn since Halo 3 faded to black five years ago -- but this time our hero bears an even greater burden.
Saving humanity is the easy part. In Halo 4, his more difficult task is rescuing Cortana from herself. She is slipping into rampancy -- a condition that plagues all UNSC AI constructs after they've been in service more than seven years. As their knowledge base expands, they eventually, as Cortana explains, think themselves to death. And that's the unexpected heart of Halo 4's greatness. The plot delves deeper into John's humanity than ever before, but Halo 4 is more about Cortana and the fight for her own -- ironically enough -- humanity.