Could it be you opened the cemetary with this key? There's a way:
You can enter Walker's back rooms. There is a key in the southwest room = works for the garden, too. JUST don't open the chest in the east room, ok?
You have to do this:

http://kiya1.via.t-online.de/images/Div_Alchem.jpg

Kiya
Or use Raze's download fix, click here