(There's a full text walkthrough for this one cause I wrote it before I realized videos would work much better. So yeah, full text here, but we also have a video)
Head left immediately after the cutscene, going along the edge of the building. Before you reach the end, ump off forward and to the left to land on the thing with the spinning fans on top. From there jump and coil to land on the next higher thing (hit near the corner or you'll miss the jump. From there jump over the fence and keep running (you don't need to roll out of the landing). Run slightly to the right of the ramp, and use LB to peform a speedvaul over the pipe and the railing, which will land you on the next roof (no roll needed). Wallrun up the platform in front of you, then jump across the gap from that one to the next one. Turn right from there, and you'll see a pipe. Jump and grab onto the pipe, then use it to swing forward and clear the barbed wire fence below you. Land, run forward, then wallrun up the building in front of you. From there, stick to the right side and run forward, and take the leap of faith towards the walkway below.
Land with a skill roll or you'll crush, then keep running forward and bust open the door with R. Turn left, then turn right with the corridor. Run through the open door, then turn left agin. Follow the corridor, then turn left once more. You'll see an elevator, which you should run up to and push the button with A. The door will open, walk inside, and push the button inside to head down. It's kinda a long ride. You'll come out into Pope's office, and you get to have a nice little conversation with your sister.
However, things go bad, as you find out. When you regain control, strafe right a bit then run forward and vault over the railing. Run forward until the path ends, then turn left. Go through that office-like area, exit through the open glass door, and go past the first left turn, hit the second. Head to the stairs at the end of the hall and take them up. RUn down that walkway until you see the elevator. Don't waste your time, it's inoperable. Turn left, then left again to go through the accounting offices. You can go the long way, or just smash through a glass pane to get to the next set of stairs. Walk to the top of those, then do a 180 and head back towards the wall. When you reach the green wall, do a wallrun to the right to land in the gap there. Jump out of the little alcove you found yourself in, and drop down to the floor again. Skill roll to land without crushing, and head to the white door that's down the little hall. Do a wallclimb, then a 180, then jump to land on a support higher up. From there, climb into the ventilation duct which is lined with red on the outside. Follow the duct until it stops, where you will have to jump up. Do so, and follow the higher duct until it drops down again. Get out of this new duct, go through the open door, and smash through the door.
Vault the railing as soon as you open the door, and you'll be doing an awesome slide down a sloping roof. Angle Faith off to the left- you're aiming for that rooftop down there. Jump off right before the slide ends to reach the next roof, and land with a skill roll. Head to the left along that rooftop, and jump to the next one from between those square blocks. Run down the ramp, turn right and jump-land with a skill roll. Slide under the pipes, run forward and to the left, and jump to the next rooftop. Slide under the protruding duct, run forward, then vault over the next, smaller duct. Run forward and ump off the ramp at the end of the building to land on one of those soft cushiony trampoline things. From there climb up on to the adacent building, and jump off of there down to the roof, had over the obstacles there, and turn left at the corner. Run along until the building on the left ends, then turn left and jump on to the fire escape there. Climb it, then run along the top walkway When the vent appears on the right, wallrun along the left side, hit RB to turn, then jump with LB to start running along the vent. Wallrun the gap, the jump back to the left and land on the roof. Find your way over the fence, then run down the gap between the solar panels, and jump off the ramp. Land with a skill roll, get up, and smash through the door. Head right as soon as the hallway allows, and vault that fence. Run through the little area, vault the next fence, and run into the elevator and activate it.
Exit the elevator and turn right, then right again. Go through the red door, then turn left, and left again. Drop down (no roll needed), then wallrun and jump to clear the gap to the next door. Go through the door, turn right and head across the bridge. Jump over the railing or go down the stair, and break open the next door. Drop down a level, then jump over the railing to slide down. Run across the bridge while cops shoot at you, then look slightly right and ump over that barrier at the end of the bridge. Head for the blue corner to the right, the entrance to a subway station with a red sign at the top of the tunnel. Enter the tunnel, then take the first left. Head down those stairs, and slide under the half-closed gate at the bottom. Turn left to head through the pink area, then right at the end of the pink tunnel. Go on straight through the blue area, slide left through the closing grate on the left. If you were too slow, head forward and there's an alternate route. Turn right to head up some stairs to a mall pink area, which opens into a wider arena. There are cops here which you can fight if you want. You can also completely blow past them as long as you move fast enough and don't break your line.
Head towards the orange stairs, and run up them. Once you're up the stairs, turn around and head for the oange garage door. Wallclimb up the garage door, head to the left and climb that ladder. At the top of the ladder, turn around and run back along the narrow strip of path. Head to the zipline, grab onto it with LB, and ride it to the next roof. Vault over the railing on that roof to slide down a short slant to the end of the level.