From the Game's Introduction:
The government tried to create a biological weapon that would self-terminate after infecting an area the size of a country. They tested it on a small area, and it forgot to kill itself.
The plague has hit. People are dying and not staying dead, or worse, mutating. Some of those who survived have gained psychic powers as an effect of the plague. The only hope for humanity is for the few who survived the initial infections to avoid being slaughtered by the hungry corpses that shamble around the cities and towns looking for their next meal.
You are one of the lucky, if that's how you choose to view it, survivors. Make friends and hope you can trust them to watch your back while you search for a fortifiable location and defend it from the hordes that swarm at night. Run to the towns and find supplies, weapons, and gear for defenses as you wait for the rescue everyone prays will come, and no one expects will.
How will you choose to survive?