This campaign is something that could be run in Beyond the Supernatural or Nightbane (though it would probably be suited to take place on or before Dark Day). The characters should already know each other by now, if not, it could certainly be an interesting introduction. The players are on their day off, be it from their mundane day job, or their faction gave them a little R&R. Occupations and OCCs can be just about anything from this little side adventure (or campaign if it's Nightbane).
The players have all decided to head off to the mall for a little R&R, either they need a few things or they just want to hang out. It's early in the winter, so snowstorms aren't a huge concern, despite the weather report of a snowstorm moving into the area. In addition, there seems to be some sort of serial killer on the loose.
While the characters are at the mall (or wherever they decided to go), the snowstorm turns into a blizzard. The characters have been snowed in. What's worse, is that, unknown to them, the killer has been snowed in with them. Slowly, people start to disappear, only to turn up a few hours later, dead. They have obviously been tortured, but it's impossible to figure out why no one heard the screams. The players must solve this mystery and stop the killer before they're next.
Notes: With this campaign, it would probably be best to use some sort of shapeshifting monster, such as a doppleganger or Ashmedai. Another fun possibility would be to have a possessing entity that moves from body to body, keeping the characters confused as to which person might be committing the grisly crimes. Additionally, it's probably going to be beneficial to have at least one government agent or investigative character. It will be a lot less fun if one of the players is psychic because they would be better able to find the cause of the problem, either thru See Aura or Sense Evil. Just a few thoughts.