Quote 13
Behind me, out on the marshes, all was still and silent; save for that movement of the water, the pony and trap might never have existed. (6.9)
Talk about the setting having an effect on a narrator. The marshy, creepy goodness of Eel Marsh House adds to the tension that we feel as Arthur goes exploring.
Quote 14
I sat up paralyzed, frozen, in the bed, conscious only of the dog and of the prickling of my own skin and of what suddenly seemed a different kind of silence, ominous and dreadful. (9.20)
Being alone offers Arthur zero consolation. It actually makes the whole thing worse. This is not a peaceful old Victorian house in a children's book; it's a creepy old Victorian house in a ghost story. Two totally different things.
Quote 15
And then, with an awful cry of realization, I knew. There was no visitor—or at least no real, human visitor—no Keckwick. (9.48)
Even Arthur's visitors are ghostly, and a ghost just can't offer the same warm hand of friendship that a real, live human can. Even Keckwick.