While at a party, the heroes and several GM characters play with a Ouija board. The sinister device reveals a cryptic message, "Bloody Mary." This is a clue suggesting heroes go to the restroom and try the old legend of Bloody Mary (Repeat the name while looking in a mirror three times, before a lit candle, and while alone). If a hero makes the attempt, horror is definitely in his future. If no hero takes the bait, James Jones, a friend at the party does.
The ritual releases a demon that attempts to possess the hero (or James), and uses that person against others. Once released, the creature must be appeased or defeated.
This adventure is written for 4 characters of at least 4th level, but may be scaled up or down depending on the makeup of the team.