Start from the Above the Baths save once you have your new sword and head down the stairwell that leads to a large cavernous area. Get through the area until you end up in a small room with Farah. There's a lever and gear in the center of the room; turn it clockwise until it clicks twice. Both doors in the room are now closed, but you have also opened a secret door that you cannot see. Go to the wall directly opposite the entrance and swing until you find a spot on the wall where your sword doesn't spark. Strike this area a couple times to reveal a hidden room. Enter to unlock the game, which is now available from the main menu.