Hi Kurt,
I played your saved game, and I know what your problem is. You need
to exit the NE corner of the Marsh (the section where you need
Demelza to enter) through a false wall and not the gate you entered
at the northern end, which is what I think you did. You have to find
the false wall in the NE corner first.
Once you go through the false wall of the NE corner, then you can go
through the false wall of the SE corner.
Hope this helped. Email me at cysk@... if you need specific
coordinates.
Good luck,
Chris