In “Undead Nightmare,” the protagonist John Marston must deal with a zombie outbreak that has infected the game’s world. He embarks on a quest to find a cure for the zombie plague and save his family. The expansion adds new weapons, mythical creatures, and a variety of side missions related to the undead theme. It’s a departure from the main game’s Wild West setting, as it infuses elements of horror and the supernatural into the game’s narrative.

“Undead Nightmare” was well-received by both players and critics for its unique take on the game’s world and the fun it provided by adding zombies to the already rich gameplay of “Red Dead Redemption.” It offered a fresh and entertaining experience for fans of the base game.