User blog comment:Reddeadbob/storys,myths and legends/@comment-184.7.55.179-20140727160622

There is a theory that says the the Undead Nightmare DLC is just John's dream. It actually makes sense because at the begining of the game Jack is telling John about a zombie story which describes exactly what happens to John. But as soon as Jack finishes telling the story John goes to bed.

SPOILER ALERT

You might ask: What about the end of the game when John gets ressurected from the dead? Well, that could be John's death dream.