I had a dream that we figured out who the Joker was and where he came from. (the Joker, as in the batman villain).

It turns out that nobody wants to think of themselves as evil. They all
want to think of themselves as a good person. Any evil that’s done, they want to put that outside of them and think that it came from someplace

So all this evil that people were disowning, it was floating around, and
coalesced, and reached critical mass, and became a demon: The Joker.

That’s why locking him up at Arkham never works. The only way to stop him would be to have everybody own up to the evil in their hearts.