This is the forum for helping you out if you're stuck or if you want to discuss the nitty gritty details of the dungeons within Mount Grimrock. Warning: forum contains spoilers!
I found the 3 buttons and they allow me to get out again after triggering the poison trap, but I cant seem to figure out how to open the door in
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Same buttons, just a different combination. I don't recall the combination, but the last button I clicked was the one at the end, on the right... and I'm not sure whether I came back to press the first one, or I pressed it before stepping into the pressure plate. I think I didn't go back, though.
Turns out it was left, entrance, right. So you have to quickly get back and forth before you hit the switch in the middle and release a second wave of poison
Thanks for clearing up that I wasn't missing anything