Heck, *I* ripped it off from an old Ravenloft module.
Basically, after scrambling for four hours trying to make up the BBG's tomb on the fly, I ended the session with, "And as you come towards the entrance, you see a figure standing there." Everybody made Will Saves, freaked out and I said, "Okay, we'll carry this on next session," making for a lovely cliff-hanger ending
Which I then frantically tried to come up with a conclusion to more interesting than, "And then he kills you all."
Came across a Ravenloft download and hey, "And then he decapitates you and taunts your disembodied heads," is MUCH more fun.