Road to Heaven is a good name.... and it comes with its own evil plot.
Road to Heaven is a town in Old West along a well traveled trail. It has your standard run of characters (set up a Fiasco of characters, just needing that tipping point for it all to go to Hell). Your characters can be town locals, farmers around the town, or people from the Stagecoach. The Stagecoach lost an axle and wheel coming into town. You all might be involved in the rescue (from along the edge of the ravine road) and bringing people into town. It will take some time to get the coach in and to make a proper axle and repairs.
There is some time for people to have some interaction, establish characters, and that bit.
People start dying.
Sure the well water tastes real funny and that might be the cause of This Crazy. However, you catch a glimpse of a person with "the red eyes" from time to time. (Red eye as it looks like when a flash goes off.)
The Red Eyes mark who is currently possessed by "The Killer". Anyone who drank the water or had sex with the red eyes can be the killer. It transfers by eye to eye contact or touch. Only one person is murderous at a time.
You might get a bit of quiet for a time, but only to find out that one of the farmsteads has been killed off by someone that was in town.
Who ever has The Red Eyes is tough to kill. Still, there are enough guns around that if you pump enough bullets in the red eyes and maybe burn the body, it will go away.
Or transfer into someone then go dormant so it can get to The West Coast. We can end the sessions with someone in the fixed stage coach looking back at the town, smiling and having red eyes.
It is a serial/slasher killer in The Old West.
The McGuffin (cause of all this) could be an Indian artifact, a curse, a parcel on the stage coach that got lost down the ravine... into the water... or the demon was with the passengers of the Stage Coach.