What I remember was that it was as though I was watching the last scene of a movie. It seemed like a school-like building to me, but it could have been a hospital or even a prison -- they all seem to share certain architectural similarities. The obvious bad guy was trapped and confronted by the people he had done wrong -- maybe conducting strange experiments or something like that; I'm not sure -- and it was clear that he was about to meet a messy end at the hands of the people he had hurt who were still alive. In fact, I never did see how he met that end: the "movie" faded out after implying a nasty end, without actually showing it. (IMO, that's a good way to do it from a cinematic point of view; suggest, then let the audience imagine what happens next.) Then I woke up, basically in tears, with strong feelings summed up as "he deserved what he got, but it's a tragedy that it came to this."
Even stranger was a strong feeling of deja vu about it, as though either (a) I've had this dream before or (b) it is from a movie I've seen or book I've read. I have no recollection of any of these things -- I don't really care for horror movies or fiction, and this seemed like a scene from such.
It took me a few minutes to calm down and remind myself, "It's not real! It's just a dream!" However, I eventually calmed down sufficiently to go back to sleep for a couple of hours.
I'm unsure that there is anything significant about this dream, but the fact that I remembered it so led me to commit it to writing.