Sometimes I feel that Autistic kids see alot more than what we can understand. For the most part, my son has no fears at all, so the only way I can tell is by the things he does manage to come up with, like suddenly seeming to take an interest in Angels! He will answer yes and no questions and sometimes will finish a sentance when I prompt him with the beginning of one, but if the subject is too abstract he won't know how to answer.
The upstairs of my house has activity from time to time, plenty of creaks and banging sounds, but there was one time when I was reading in my bedroom - at the time I only had the first child (who was asleep in her crib) and I was still married - my husband was in the living room on the main floor, I heard what I thought was my husband come up the stairs and stop at the doorway to the bedroom, so I turned to look and noone was there. I went downstairs to question him, only to find him fast asleep on the sofa. Another time I was in the bathroom looking in the mirror (which is right beside the door) and it felt like a cat had jumped into the room or was thrown into the room. It went past my head and there was enough force that it caused me to jump out of the way. When I looked to where it should have landed, there was nothing, but there was nothing else out of the ordinary either. The only thing I could think that it may have been was the cat that we had that was killed by a couple dogs. She and I had a very strong bond, and she even came to me in a couple of dreams that were very emotional and even thinking about them today makes me teary eyed. My daughter many years later, tells me she had the same experience of someone coming upstairs too. Another time I woke during the night to hear some really loud electric guitar music, it sounded very etheral and I was the only one waken by it, I have no doubt it was only meant for me, but I'm not sure why. lol Those are just some of the "upstairs" experiences, so I think it's the entire upstairs and I'm just more used to the experiences but, I still keep a light on. However, my worst fear is for someone to break into my house while we are asleep, so I think those type of safety reasons concern me most, and the fact that there's usually such a mess in the hall that I need to see where I'm going if I'm suddenly needed through the night, so I don't break my neck getting there lol.