After I had done that I went upstairs to my study, but why I did so
I do not know.  The window of my study looks over the trees and the
railway towards Horsell Common.  In the hurry of our departure this
window had been left open.  The passage was dark, and, by contrast with
the picture the window frame enclosed, the side of the room seemed
impenetrably dark.  I stopped short in the doorway.