This is a relatively brief mission, and you'll want to bring along the ability to hack steam vents to make it briefer still. In the Mad Mile area, near the far north side of the map, you can find your next campaign mission. Go there and accept it.
Eliminate all enemies.
You have to clear an area of enemies, and there are quite a few of them showing on the radar as your first objective is set.
Head forward toward the restricted area. There will be a few guards on the perimeter, and more as you approach the center. You can approach a truck parked along the edge and find cover behind it, then look to a camera on a nearby pole. Head into the area by way of the series of cameras, using explosive plates and panels to take out the enemies. Don't use any of the steam vents, though. You'll want those in a moment.
If you aren't able to take out all of the enemies using the environment, you can run and gun to take out the last few, or hit them with shots from a sniper rifle. Once you clear the enemies out of the area, you'll gain a new objective.
Defend against reinforcements.
Vehicles will come pulling up to the building. You can use your ability to neutralize them as they arrive, by firing steam from the vents to make them explode. There are two vents along the building that can take out both vehicles before the men have a chance to pour out of them and be a nuisance.
If any of the vehicles do survive, a few men will come out in search of the threat to the facility (that would be you). Make sure that you prevent them from calling for reinforcements as you tend to them. They should fall pretty easily, and you may even have explosive plates left to help with that. Then you'll gain a new objective.
Find Jackson.
Jackson's beacon appears, so make your way to that next.
Head around to the back of the building, on the upper balcony level, and you'll find more stairs leading even higher, to a door. There's a panel next to the door, so hack it. Head through the door and down a hallway, then right to find Jackson where he is hiding.
A scene follows, and then a second one. As that ends, so does the mission.
NEXT: Act II: Planting a Bug
