Voldemort knows. Harry Potter and the Deathly Hallows Part 2
Harry Potter: He knows. You know who. He knows we broke into Gringotts. He knows what we took. And he knows we are hunting Horcruxes. Hermione: How is it you know? I saw him. You let him in? Harry, you can't do that. Hermione, I can't always help it. Well, maybe I can, I don't know.
Ron: Never mind, what happened? Well, he's angry. And scared too. He knows if we find and destroy all the Horcruxes we'll be able to kill him. I reckon he'll stop at nothing to make sure we don't find the rest.
There's more. One of them's a Hogwarts. What? You saw it? I saw the castle and Rowena Ravenclaw. It must have something to do with her. We must go there now! What? We can't do that. We've got to plan. We've got to figure it out. Hermione. When have any of our plans actually worked? We plan, we get there, all hell breaks loose.
