Who was at the door trying to get into Nathan and Haley's house and leaving the doors open places in season 9? Did they ever say?

I don't think they ever said, but I just assumed it was Clay and his sleepwalking.

Dan? Because of episode 5 Season 9?

HALEY: Well? Answer the question, Dan. Du sagte Du Lost everything in the fire, so why do Du have this? And all that money... why do Du have that? Was it not an accident? Did Du start the feuer yourself? Oh, my God. Du did! Du started the fire! I trusted you. I let Du into my home. I defended you, and Du lied to me, and Du took advantage of me! And the doors... the doors here and at the cafe. Was that you, too?

DAN: Haley, will Du let me explain?

HALEY: What else are Du lying about, Dan? Where is Nathan? What did Du do to him?

It was Dan Scott, Nathan's dad.