I'm having a problem opening the secret door behind which supposedly rests the third tablet. I am in the "Y" shaped room, and have one glowstone. I opened the right hand door and flipped the switch, then removed the glowstone, moved it to the left door and flipped that switch. What is supposed to happen? Based on my map, it looks like there should be a secret door where the picture is above the pool of water between the doors. However, nothing seems to happen, and I can't find the last tablet. Can anyone help me with this?? Thanks.

The trick here is that you have to also keep both doors OPEN - when you manage that, the alcove with the chest and tablet piece should also open!

(and you are correct about where it should open - by that pool)

Wyv