Haunted curtains! It's like a perfect triple scoop MRJ phobia ice cream cone: hair, fabric, and everyday things turning out to be spooky. When you say it plain--this story is about possessed curtains--it sounds absurd, but I don't think the tale itself is.
James tells this story as if it were a detective story, with a very detached narrative voice that collects evidence and is rather fussy about what goes into the document. I think this style rather serves to make the supernatural part of the story quite creepy.
What did you think of the use of hair (capitalized--Hair) as the main element of horror? MRJ is the only writer I know of who can make hair so completely creepy and horrifying. It gives me the shivers.