Night Manor Help

Anyone who has completed this, can I get a subtle hint on how to get into the basement? I'm assuming I need an iron key, but have had no luck on finding it.

Edit: Figured it out and finished the game. What an awesome little game. I was obsessed with games like Shadow gate and Deja Vu on the NES and had this been around back then, I would have been equally obsessed with it. Easily my fave UFO50 game so far.