A few observations and spoilers
Ok, first of all, seriously, the villain's name was Dr. Freudstein, like Sigmund Freud+ Albert Einstein? Man, this name is seriously screaming "I'm a mad scientist with German-Jewish roots"!!!!! :-)
Anyhow, just a few points that have been brought up already but whatever. I know Fulci films aren't supposed to make sense, but this one easily could have. It could have been The Others meets House on Haunted hill. But so many unresolved questions... The babysitter's mysteries. Her and Norman exchanging creepy stares. Norman coming town with a daughter(WTH?). The creepy little girl that only the kid could see. Almost none of these were necessary.
I liked the ending though. It's the only part that did make sense, but only after I had seen the Sixth Sense and the Others. The boy dies and gets transported into the spirit realm... What happens when someone finally kills Dr. Freudstein?(Like, with a bazooka or flames or a phaser in the 24th century, whatever)... Does he appear in the spirit realm as his human self, or zombie self? Or does he go straight to hell?
A fun ride, and( please don't murder me) could make a decent horror film today, with a good director.