From Halopedia, the Halo wiki
Opens to John-117's malfunctioning HUD. His energy shield recharges. His view is covered by steam. His motion tracker indicates an enemy approaching him. He looks up and sees a figure tinted with orange lights approaching him — the Didact. Cut to the back of the figure. John is constrained on a containment field device. The figure stops in front of John. Cut to John-117's HUD. The figure scans John, inducing pain on him. Cut to John's armor as the figure scans him, displaying his skeletal structure. Scene zooms into his head:
John looks behind him and sees a woman waving at him. The woman flickers into Cortana in a dark background momentarily.
Scene zooms John when he is being abducted by ONI agent. Another agent, holding a flash clone of John, proceeds to put the flash clone down on John's bed. The first agent, holding John, leaves the bedroom; another agent holding a data pad stands just outside.
Scene zooms to John's point of view as he undergoes the SPARTAN-II augmentation procedures: a surgeon looks at him. He looks over to his left and sees SPARTAN-073 struggling from the medical instruments around him. He suffers from the side effects and dies on the hospital bed, with the medical technicians attempting in vain to revive him.
Scenes zooms to John's point of view: he wakes up from the procedures and sits up. The Spartan looks at his badly cut forearms. John tightens his grips. He looks at his fists, which are also badly cut. Cuts to John looking over to his right: there are countless other beds, most of which are empty.
Scene zooms to a cavernous room where engineers are helping John into the MJOLNIR Mark IV armor. The chest armor clasp on. Cut to John's point of view as one of the technicians places the helmet on his head.
Scene zooms to John's HUD as he observes a line of Promethean Knights patrol a path below the cliff he is standing on. Cuts to John as he throws a frag grenade down to the path. The grenade explodes, destroying three of the Knights. John jumps down, firing his assault rifle. He lands on one of the Knights, crushing it. He picks up the Knight's scattershot and runs towards the one in front of him, firing the scattershot. The second Knight disintegrates. He continues, tackling the third, before a blast propels him to rock wall. John struggles to stand up, but a Knight pins him to the ground and opens its faceplate, showing John its screaming orange skull.
Scene zooms out back to present as the Didact completes his scan on John. The Forerunner looks at John face-to-face.
Cuts to an "unbound" Didact icon, glowing orange and spinning upside down.
AN ANCIENT EVIL AWAKENS
The icon pulses with bright orange light.
The trailer was filmed in Prague, Czech Republic. Tim Miller, whom Fincher worked with on his 2011 American adaptation of The Girl with the Dragon Tattoo as its visual effects lead, worked with Fincher as the director on the project.
Conan O'Brien and Andy Richter, who lend their talents as Infinity crewmen, reprised their roles from the game's campaign for the trailer. Scanned premiered during the airing of the October 18th, 2012 episode of NBC's evening talk show Late Night with Jimmy Fallon and was subsequently made available on other media outlets and platforms following the broadcast.
As the camera zooms into John's skeletal head, the Wilhelm scream can be heard.