Red Dead Redemption: Undead Nightmare

Undead Nightmare is an alternate timeline expansion that adds a new full-length story in a zombie horror theme and reworks the base game's environment to appear dark and spooky. As corpses begin to rise from the dead to become flesh-eating zombies, some of the living go into hiding and others become hostile. Marston seeks to find the plague's cause and its cure for his wife and son. (wikipedia.org)