Jump on the boxes and climb until you reach another lantern. Approach the edge and jump onto the boxes when they tilt to your side. Then, climb up using the chain and jump onto the platform.
Use the bars and protruding edges to climb up. Grab the switch and pull it down. Now go to the lever and pull it to the right. When the boxes on chain are next to the platform, pull the lever left, and quickly jump onto the boxes. You need the right momentum to do this.
When you reach the other end of the room, use the chain to climb up and enter the room with file drawers. Pull the lowest drawer out climb it, and pull out another. Repeat that until you're able to jump from the top and pull down the switch to turn electricity off. Run through the door on the left and light up another lantern.
Push the weight down, jump onto the line and go down. Avoid the falling worms - don't touch them, remember. Go through the bars on the right. There's the eye again, with its ominous beam of light.
When it's safe, run towards the crates in the middle. A cart will roll towards them - walk alongside it to stay in the shadow. Wait until the eye's not looking and go through the door.
Go on the footbridge but be careful - it will begin to split. Sprint ahead and jump to the other side. Then quickly jump on the crate and enter the platform. Go through the door into a dark room and follow the leprechauns. This will be the conclusion of this stage of the game and unlock the achievement The Prison.