Instructions
Locate and defeat the first and second Poe Sisters from the West and East Stairwells in the dungeon. Recover the compass from the East Stairwell. Go up the stairs in this room and proceed through the locked door.
Take a step forward and listen to Navi's warning. Drop to the floor and await the Wallmaster. Avoid its attacks and eliminate it.
Go up the ladder to the right of the doorway you entered. Head through the door at the top and proceed down the hallway. Kill or ignore the Green Bubbles, then enter the door at the end.
Ride the rotating platforms, then shoot an arrow through the flame and into the frozen eyeball switch against the right wall. Return to the previous room after activating the switch.
Go to the opposite end of the hall and drop down to the floor. Coax the Wallmaster out of hiding by running around the room, then destroy it after it lands. Jump down the pit in the right corner of the room.
Turn to the south when you land, and take notice of the gaps in the ceiling. Proceed forward, then stop when Navi speaks. Locate the next gap as the ceiling comes down. Pause at each gap as you continue south, eliminating any Big Skulltulas you encounter along the way.
Step on the switch halfway down the hall on the right side. This will open the door at the end. Enter this door when you reach it.
Shoot an arrow at the picture of the Poe Sister on the wall. The puzzle blocks will come down from above. Locate the block that doesn't match the others and push it off to the side. Push the other four puzzle blocks together and the third Poe Sister will appear.