Hi Katie. It has been a long time since I played this wonderful, frustrating game. I used the mine-maze maps and other maps of the castle a lot from balmoralsoftware - but there is none for this lab. As near as I can remember try this - from the table where you placed the girl, go back to the workbench? where you put together that little parachute for the crystal and threw it out the window, then turn toward your left and keeping on that side of the room try to find the dumbwaiter. I could be misremembering this but it seems that is how I found it.
Love, Betty Lou
I am 'the HAT lady"! and "who loves ya BABY?!"