Click on the chain so that you see that small octagonal icon, and then immediately click on the hole in the bottom of the door. You don't see Sadja actually lift the chain, but you see the outside of the door and sounds of grunting as the chain/ball gets put through the door.
If memory serves, I clicked all over to get the tremors achievement - not just the wall where Sadja is looking through the hole, but on the ground and the wall beneath the hole where he threw the brazier to get the tremors achievement. Use your spacebar to show the hotspots to see where to click.
Thanks, MaG, for the link to the walkthrough. I appreciate it. They're not that far yet, but will be eventually.