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

DAN: Haley, will te let me explain?

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

It was Dan Scott, Nathan's dad.