Act 3: Belly of the Beast - 1. Dark Skies, Dark Shadows

Proceed all the way to a well-lit door when you round the corner. No fighting on the way. After the scene, go the left side of the door for some Frags down a little path.

Continue following the larger path, ignore the scares, and there is some ammo and Lancers laying around. When you reach the open area be ready for your first skirmish with the Dark Wretches. Just know that they blow up after you kill them, so be careful. About eight or so will rush you two. Proceed and their is some ammo behind the van. Once you get to the start of the narrow path, you should anticipate three more Wretches.

Continue along the water's edge. Notice the huge bricked buildings. You want to go behind the second one that has a big red COG symbol. Go to the back and go to the very end of the dock for COG #19.

Come back out and go to the third huge building. Press the green button and then hurry back to the side of the second building. Go inside and press the button inside the elevator (its on the wall) and you should avoid the lone Dark Wretch. Follow the path to the window and proceed.