Right after the fall, pass all the worms and make sure you don't touch them. At the end of the room, push the door and quickly escape the slimy things. Jump to the other side of the bridge and take the ladder up.
Next, walk on the small plank and go up the stairs again. Cross the bridge and keep going up, until you reach the wheel. Turn it and then run to the right - you only have a moment before the door shuts.
In the next room, approach the hatch underneath the light bulb and open it. A leprechaun will pop up - follow it. Jump on the white line and climb up. On the other side, light up the lantern and go through the door.
Close the door and you'll see the leaver - move the chest with toilet paper till it's underneath the lever and jump on the chest. Then sprint to the right - go into the next room. You have to run through it and cross the barred door before the electricity returns. If you can't make it, use the drawers and the hatch to get back and try again. If you succeed, you will reach a room with many doors. Bypass it and you'll reach a room with a huge window.