During the campaign of Halo 3 i got really confused and had no idea what was happening . So we activate the ark and then go through a portal back to our dimension … |:o … If anyone can help me understand the storyline , it would be greatly appreciated .
Chief crash lands back on Earth. UNSC forces pull him out and get him to Crow’s Nest, an old military base that has been used as an HQ during the Covenant attack.
The Covenant want to activate the Ark, so they can fire all the Halo rings. The Elites were betrayed by the Prophets, and some now fight on the Human’s side. They believe that the structure the Covenant is unearthing outside Voi is the Ark.
The launch an assault to stop the Covenant, but are too late. It is revealed that the structure was not the Ark, it was a Portal. The Covenant go through the Portal as a Flood-infested ship arrives.
The Elites show up to glass over the Flood infected area, and takes team of UNSC forces through the Portal to stop the Covenant and find a solution to the Flood as the rest of the UNSC remains back to hold off the Flood.
On the other side of the Portal is the actual Ark. UNSC forces clear a landing zone for their Frigate and find the location of Truth, the Covenant leader, who is in the Ark’s control room.
They bring down a barrier around the control room, but Johnson is captured. Then the Flood-infested High Charity appears, apparently skipping Earth entirely. They quickly finish off Truth, though Miranda is killed trying to rescue Johnson. They learn that the Ark is making a replacement Halo, due to one being destroyed in the first game.
The Chief goes into the wreckage to rescue Cortana, who has the Index, and they go to activate the ring to finish off the Flood, as the Ark is out of range of the galaxy. The ring is unfinished, and Guilty Spark realizes that activating it will destroy the ring again, so he kills Johnson. Spark is defeated and Chief activates the ring, fleeing to the nearby Frigate and barely escaping.
The Frigate is torn in half as the Portal collapses, with the Arbiter making it back to Earth but the Chief being stranded in space.
Cue, Halo 4. Well… almost 5 years later.