there is a sewer key..before you can cross the bridge..you have a choice of stairs to the
left or right..the stairs to the left take you down into a room with a channel of water
between you and the chests (and the sewer stinker things) if you dive into (and under) the
water..you will find a secret p***age..this takes you into another room and in that room
you will find the 'sewer' key. This key unlocks all rooms in the sewer.