Very nice! I like that one alot. That's the route I would take, it's simple but very creepy. I know alot of Game Masters that get too involved in everything. A plot starts with every simple conversation. Pretty soon the characters are trying to decide which way to go and find that thier plates are over filled. When your players feel like this and then you throw in an adventure that you want them to bite on, they either bite and feel even more overwhelmed or you can't get them to bite on anything until they resolve the plethera (sorry for the spelling) of other avenues you've given them.
As a player I love to feel that I have the freedom to do what I want to do, and most of those things I create myself. What I don't like is when I feel choked by the game master/marshal's plots to the point where I don't have that freedom. In this situation (demon poker game) the plot is inside, not at the door. It should be amusing but simple! Clint hit the nail on the head.