Red Dead Redemption: Undead Nightmare is an expansion for Red Dead Redemption that introduces a zombie apocalypse to the game’s Wild West setting. Players take on the role of John Marston as he navigates a world overrun by undead creatures. The expansion features a new storyline, unique missions, and a variety of zombie-themed challenges. It includes new weapons, items, and a modified game world with a horror twist, offering a fresh and eerie take on the original game’s open-world gameplay.