Red Dead Redemption: Undead Nightmare is a standalone to the 2010 . It adds a non- -themed campaign, two modes, and cosmetic additions to the environments and characters of the . Set in an alternate timeline from the base game's story, the plot follows returning protagonist , a former outlaw who sets out to find the cause and possible cure to a zombie plague that has infected his wife and son. Marston liberates towns overrun by the undead and assists with along the way.
, the game's publisher, had a long-standing interest in creating a zombie game. They found the Red Dead Redemption universe and its American countryside to fit the cinematic heritage of the horror film genre. Rockstar wanted their additional content to function outside rather than within the base game's story, but draw on its characters and atmosphere. The company released Undead Nightmare as for and platforms on October 26, 2010, and as a retail disc bundle with other downloadable content packs in late November.
Undead Nightmare received generally favorable reviews at its release, and the retail disc sold two million copies by 2011. It was praised as a model for downloadable content and named among the best of the year, with top awards from the 2010 and in this category. Critics praised its production values and handling of the zombie video game motif, and noted its lightheartedness compared to the main game, although some reviewers struggled with the game's character movement controls and found the combat unvaried. It is retrospectively considered to be among the best downloadable content packs on record.