Keppel Stuart, M.D., F. R. S., awoke with a start and discovered himself to be bathed in cold perspiration. The moonlight shone in at his window, but did not touch the bed, therefore his awakening could not be due to this cause. He lay for some time listening for any unfamiliar noise which might account for the sudden disturbance of his usually sound slumbers. In the house below nothing stirred. His windows were widely open and he could detect that vague drumming which is characteristic of midnight London; sometimes, too, the clashing of buffers upon some siding of the Brighton railway where shunting was in progress and occasional siren notes from the Thames. Otherwise-nothing.