Walkthrough for Filth and Other Entertainment of Red Dead Redemption: Undead Nightmare.
1. Go to the green question mark at the Plainview in left down of the Rio Bravo.
2. Clear the city and meet McKenna in the green question mark.
3. He asks you to bring him a Retcher. This zombie is the one that spits blue and green acid from his mouth. You can find this zombie in one of unsafe cities that are under attack, they are marked with question mark in the map. Remember that if you save the city, the Retcher zombie will fade away, just capture one and go back to McKenna.
