I suddenly have an awesome image:

A small quiet town. Over the last few nights it has gotten even quieter. Most of the homes have become derelicts as their former residents now walk the streets.The characters are standing in the center of the street in this silent neighborhood. All of them are beat up and worn down. A few haven't slept for days. They stand waiting, in the distance, the sea of once-living shuffles slowly toward them on all sides. A halo of kinetic energy burst around a few of the players heads as they strap down into their now chainsaw retrofitted PK-Frame Utility Walkers.

This towns former population was 16,223. They have yet to find a survivor. They're in for another rough night.

Now comes your part: Why?

Why are the characters here? Whats going on? What's the lead in?

Keep it Sci Fi and keep it horrific.

There's a death camp over the hill run by aliens at war with humanity who have occupied parts of the earth. They're experimenting on captive humans, infesting them with parasites to produce zombie soldiers to wear down supplies and morale in the survivors.

When the PCs finally get through to the camp to destroy it, they find that the aliens are not there at all, in fact. Collaborator humans run it, torturing and murdering their fellow humans in the hopes that they will be allowed to survive once the aliens win.

A borg like, nanotech alien consciousness/weapon has infected the town, and seeks to spread all over earth, turning the planet into a resource for their conquest of the universe. There is an opposing force that wishes to take earth for it's own ends, and they are helping the PCs fight the nanotech consciousness so they can use the human race as an energy source, for they are incorporeal psionic entities.

Quote from: Dominus NoxA borg like, nanotech alien consciousness/weapon has infected the town, and seeks to spread all over earth, turning the planet into a resource for their conquest of the universe. There is an opposing force that wishes to take earth for it's own ends, and they are helping the PCs fight the nanotech consciousness so they can use the human race as an energy source, for they are incorporeal psionic entities.

Oooh, drop the aliens and make it the government.

The PC's are the results of a continuing Top Secret, MK-Ultra program. However, when our own government tested out their new nano-biological weapon on a small town, things got out of control. The group, who are all Psychics or Telkineticists, originally there "just to observe" are now fighting for survival.

You could go with something like The color out of space by HP Lovecraft. A strange otherworldly creature composed of color not of this earth is slowly feeding on the local inhabitants, leeching away their youth as well as their very lives.

Quote from: RockViperYou could go with something like The color out of space by HP Lovecraft. A strange otherworldly creature composed of color not of this earth is slowly feeding on the local inhabitants, leeching away their youth as well as their very lives.

 Sounds almost like a Stephen King story - just with better writing.

- E.W.C.