Walkthrough for Dinner for Two of Red Dead Redemption: Undead Nightmare.
1. Go to the green question mark between Armadillo and Cholla Springs.
2. Help survivors in clearing the city and then meet Marshal in Sheriff's Office.
3. Go to M mark in the city.
4. Go the horse pen (On top of the city if you look at the map) to and kill Jonah and Eli.
5. Get back to Marshal in Sheriff's Office marked with M.