hi, i'm just starting in act 1 and got all the way to citadel level 8, which takes me back to level 2. anyways, on level 2 there's a locked door to a room that i can't seem to open. i've tried to do a search/walkthrough but can't find any answers. help anyone?

it's the red X on the south west corner.

http://us.f1f.yahoofs.com/bc/42a8b920/bc/My+Folder/citadel2.jpg?bfknhQBBqdUn18HN