I need to get into the Lab to get the Dark Light and the door disappeared. The professor assures me there is another way in, but I can't find it! How do I get into the Lab?
Go to the room a floor above it, the Parlor, where the green digital clock is. Go into the fire place and you'll land in the lab.
In general for this game, if you're trying to get into a room but can't for some reason or another, the room directly above it or directly below it will be the way in.