Wow, OK. That has happened to me only one other time. Had a player want to play, I make room and start thinking of way to tie their story in and they bounce. It's fine. We wamt to keep runing with 2 or go back to one. I'm good with either(I vote one myself).
Let's roll with plane crash. You are all in Vegas-lite city(Vegas-esk city would be a very on point city for the Mist to hide strange things in, as well as keep those inside from leaving) you are each there for one reason or another; gambling, convention, shows, vacation, etc. As the sun has set and the last remaining streams of its light kiss the sky above, darkness begins to take the night. Darkness? Here? The denizens and tourists begin a light commotion as blocks of the city stay dark. Soon after the sun reach falls from the skys grasp the city erupts into noise, explosions, fire, theft, screams, fear and epicaricacy.
The media claimed a plane crashed into a power station cutting power from blocks of the city, but that doesn't explain all the weird and violent stuff that went on.
That may need a couple tweeks but Ithink that hits a lot of the points mentioned so far. Anyone got more to add, maybe alter some? My word is not final at this point in the road.