Chapter 6 (or 7?) Rykros Help

I'm stuck at the begining of the Rykros Dungeon in chapter 6 or 7 (can't remember which chapter I'm currently on).

There's three barriers that are turned off to access the door in the central block, but I've only been able to turn off two of the doors by leaving two characters on the switches in the west and east blocks. However, I can't seem to find the third switch to shut down the remaining barrier...

Anybody know where it is?

Go south of the barrier and clear out that room.

Totally mistook the south block as the entrance. :P

Thanks!