The Hunter and the Hunted
From Halopedia, the Halo wiki
First shown at Microsoft's E3 2014 conference, the trailer features a remastered cutscene from the level Cairo Station from the Halo 2 campaign. The trailer shows John-117 dragging a Covenant antimatter charge through one of the hangar bays in Cairo Station to "return" the bomb to a CAS-class assault carrier. Arbiter Thel 'Vadam provides a voice-over for the trailer and it is revealed that Spartan Jameson Locke is searching for the Master Chief.
As the charge scratches across the floor, the Master Chief opens a door to enter an airlock. He looks through a window to view the space battle occurring over Earth. He opens the airlock door and holds onto a handle and the bomb to prevent being sucked out of the station. He looks down at a Covenant assault carrier and launches himself, with the bomb, from the station.
Master Chief floats through space, towards Earth. He aims the bomb towards the carrier. Nearby, a Marathon-class heavy cruiser is destroyed by an off-screen vessel while the carrier fires its ventral beam at the planet's surface.
The Spartan continues through the field of debris from the destroyed cruiser. Several Longswords pass nearby.
The Master Chief nears the assault carrier, as several Seraphs fly under it.
Cut to Jameson Locke viewing the Spartan entering the assault carrier with the bomb, as several Longswords fly beyond the ship.
The Master Chief activates the charge and kicks it into the carrier. The entire ship bursts into flames and explodes. The Master Chief covers his visor as the explosion's light blinds him.
Cut back to Locke closing the holographic video, with several more still active in the background. He walks towards a window, which it opens and reveals a desert world, Sanghelios, and turns towards the Arbiter, who is standing at his right. The Arbiter's face reflects in Locke's visor.
Cut to a close-up of Master Chief's original Mark VI helmet:
YOUR JOURNEY BEGINS