Nothing is more suspenseful (and Hitchcock's business was suspense) than a person on the stairs. Ooh, don't go up there! Ooh, don't go down there! Stairs are transitional. Uncanny. In Limbo. As Christopher Robin says of
his special place halfway down the stairs-
"It isn't really
It's somewhere else
Unsurprisingly a lot of hauntings focus on staircases. You lie in bed and hear the footsteps come creaking up- to stop (if you're lucky) just outside your bedroom door. One of Hans Holzer's "true" stories has a woman turning on the stairs to see the bloodstained figure of a man below her reaching out his hand for help.
I remember crouching at the top of the stairs to hear my mother and father arguing at the bottom. "You are the most selfish person I have ever known," she said. In that moment I realized that they and I were separate. They could tear one another to pieces and it didn't have to affect me. My heart stopped hammering and I felt peaceful. I had a soul of my own. There were stairs between us.
My grandmother told me of a flight of stone steps going down to the river in her home town of Maidstone. Folklore said that it you climbed it 13 times you would be doused with a bucket of blood. Of course, no-one had ever actually put this to the test...