Unlimited ammo.
You're one of Earths remnant soldiers! captured by the evil mutant army known only as the BEASTS. You're set to be executed but low and behold one of the few humans left behind saves your sorry @$$. If only for a little while. The virus in your blood makes you a ticking time bomb and you only have a few hours left, Put up your last stand and fight the BEAST army in this tactical shooter.