Amnesia: The Dark Descent Walkthrough:Back at the Initial Cistern Room

As soon as you exit the Control room, look to your right and pull the lever. The other bridge on the right side will finally start to lower down. Unfortunately it will get stuck midway! Something’s jamming it.

Since something is jamming the bridge, we’ll need to hit it with something hard to unjam it. Go to the end of the platform and climb down the stairs. Find a rock or something on the ground, and throw it up back to the higher platform. Climb the ladder and find the rock that you just threw. Now grab the rock and aim for the circular thing where the chains are attached on the bridge. This should cause it to unjam and the bridge will finally be lowered. *

Now that the bridge is unjammed, it’s time to cross it and go through the door and into the Morgue!