Today, the American North East coast, a city is suddenly hit by a massive cloud of smoke.
Mysterious swirls of this black smoke appear and infect everybody.
This new disease is spreading all over the city making it a place full of sick people sunk into a comatose state.
As they mutate into strange creatures with various powers and group behaviours, they start to become violent and invade the whole city.
The player is a survivor who will try to stay alive and wipe out this scourge from the city.