Having tightly bound and gagged the entry guards, the party moves to the east passage, and follows it carefully, not entirely trusting the word of the men left behind. Good to their word at in least some respects, you find a northern passage that contains three very small doors with bottom slits (like you'd feed a wild dog through, or perhaps, a prisoner), further north is another door, and then the passage turns to the west. That passage has a southern door that seems likely to enter the same room as the other door just as described.
ooc: for ease going into the weekend, here is the map with more detail than you've actually seen yet :-)..