I heard (on this lecture series I can't shut up about), that true horror, is becoming unanchored from sense making (or some such thing, I'm butchering wording).

Example given was The Shining (paraphrasing as a quote):

"I was watching, thinking it was metaphor for alcoholism, as I know alcoholism is a big thing for Stephen king. Yada yada, some brief examples that support the interpretation. Not that scary. But, There's a scene where wife tricks Jack and locks him in utility closet. He protests, and at some point hears voices, and talks to them, and the door clicks/unlocks. Right then, I felt the horror take hold"