The next hall leads to the last LIMB Clinic in the game.  If you can spare the
credits, buy the two last Praxis Kits, along with Hypostims and Typhoon Ammo.
Continue through the hall when you're done.  It'll be around this time that
William Taggart asks for help.

Go through the doorway and hop onto the black beams, then look to your right
and jump onto the blue scaffolding.  Move towards the building's wall and hop
onto the edge, then crawl to the far side of the area.  Drop down.

FINDING WILLIAM TAGGART
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Go through the doorway by moving over the beams.  Head through the hall, but
beware when going down the stairs; there are cameras up ahead.

As the camera looks away, turn left and drop down next to the pipes, and hug the
wall, staying out of sight.  Moving to the end of the pipes leads you to a vent
cover; head inside and go straight ahead, ignoring the shaft to your right for
now.

This leads to William Taggart's room.  Speak to him twice to get all of the main
dialogue,  then exit the room.  Loot the corpses, go around the corner, and move
the metal crates away from the wall to reveal a ventilation cover. Head inside
and you'll find yourself back at the pipeline area.  Backtrack the way you came,
avoiding the cameras stealthily.

Here, crouch and move to the railing south of you.  You'll need to Icarus
Landing System along with cloak for the next maneuver:  While crouching, head
west and approach the scaffolding.  Turn on cloak and hop down the railing to
your right; you should fall down the long, big ventilation shaft.  There are
crazies down below, so immediately go through the double doors and shut them
behind you, then go around the corner and turn off cloak.