You were one of the survivors with Killer and the others. But when you tried to go out with them to find some supplies, the infected spotted you and chased after you. But then, Killer got seperated from the group. So after you managed to lose the infected from your track, you immediately tried to find Killer. After a while, you finally found him in the corner of a room.. curled up... trembling. You tried to ask him what's wrong.. but when he faces you.. you immediately saw the bleeding scratch on his arm... and saw he was crying. You instantly knew he was infected...