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

DAN: Haley, will toi let me explain?

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

It was Dan Scott, Nathan's dad.