Grimrock

I am stuck in sewer. Not open the door that says "Headquarter". And, I can not go to an island located near the door. I looked all or switch is not in the wall. I'll be good I do? all the torches must be blown out in that part of the sewer, then appears a magic bridge I can proceed! Thank...

I am stuck in sewer.
Not open the door that says "Headquarter".
And, I can not go to an island located near the door.
I looked all or switch is not in the wall.
I'll be good I do?