Halo Walkthrough: Fourth Floor: Tools Guns, Keys to Secret Weapons
You come into this level with a fight already going on. Go straight across to the health. Use the shotguns on the baddies. Head down into a ditch, through and up the other side. More biggies. There's health in one of the other ditches.
Now you hit a big door and the music swells. Always a bad sign. Get your shotgun and grenades ready, there are a TON of bad guys here.
Go in to the big light. "The energy barrier surrounding the index will deactivate when we reach the ground floor." Oh swell.
And yes, you get the index at the bottom! He takes it from you though, and says you have to hurry. He then takes you right to the control room.
You're still on the same 'game level' but now you're at the control room spot. You start to reintegrate the index, and Cortana appears to yell at you. You learn that Halo was constructed to destroy all life in the universe. Apparently there was no real way to stop flood, which lives by feeding on live beings. So they figured they'd starve Flood by killing all live beings. Doesn't make a lot of sense, does it? If they don't mind all live beings being dead, why not just let Flood kill them? They'd die out after that anyway.
