I won't spoil the ending for you by telling you more than that but I will tell you that King has ones again succeeded with one of his short stories. He tells it in a good way, he set it up for us and then in the end he takes it in a totally different way than we anticipated. And I love it. I love it when King surprises us and makes us think we have it all figured out and then tells us "no, that's not it, this is how it is". And that is exactly what he do here.
The Dune is rather short and I read it in one sitting but that really don't matter. If the story is good, and I think The Dune is, that's the important thing. And after all, this is a short story. So, check it out in Granta when you get a chance. It's well worth reading if you ask me.