In the wake of a viral outbreak the world had never forseen, the majority of the world has been overrun by zombies, and other creatures mutated by a virus left totally unchecked. One of the last few known bastions of civilization is a tightly-quarantined Manhattan Island. Life goes on with a diluted sense of normality in the city, albeit with a heavy military presence by a group known only as Division-7. Travel onto and off of the island is heavily monitored to the point where the vast majority of the civilian populus has little to no knowledge of the outside world, peacefully unaware of the immense threat mere miles outside of the fences and barricades.
The strong arm of the military regime in this new world is what brings us to the plot of our story. Each of you have been convicted of a serious crime, regardless of actual guilt. A serious crime in this world, unfortunately, could be anything from murder, to trespassing on Division-7 property, to stealing from a particularly rich family. The punishment for all but the most petty offenses, due to the overpopulation of the city’s few prisons, is to be exiled from the colony altogether.
The six of you are the sole passengers of a helicopter headed to a location referred to as “Drop Point C”, hours away from Manhattan. Why you weren’t relegated to Drop Point A or B is of little concern, as the only thing waiting for you upon landing is a haphazard assortment of improvised shacks and would-be abandoned buildings surrounded by a tall, gated barricade. A few colonists mull about the town as your chopper descends to a barely-marked helipad, seeming wholly unphased by a new shipment of convicts.
Welcome to your new home, Citizens.
After that, take a look at your wiki. There is some more helpful info there.