Starting with the single-player, you reprise your role as John Marston. You're called in to help out on a supposed plague that is infecting the local folks and turning them into stark raving undead. Broken up into different types of zombie classes (Bolters, Bruisers and Retchers), you're up against what some might consider hopeless situations. In reality, you're in the same world that Marston is use to in the original RDR with the exception of zombies. The world really is divided into three things in the Undead Nightmare pack: the living (usually hiding), the dead and the undead.