When the Inspector had taken his departure Stuart stood for a long time staring out of the study window at the little lawn with its bordering of high neatly-trimmed privet above which at intervals arose the mop crowns of dwarf acacias. A spell of warm weather seemed at last to have begun, and clouds of gnats floated over the grass, their minute wings glittering in the sunshine. Despite the nearness of teeming streets, this was a backwater of London's stream. He sighed and returned to some work which the visit of the Scotland Yard man had interrupted. Later in the afternoon he had occasion to visit the institution to which he had recently been appointed as medical officer, and in contemplation of the squalor through which his steps led him he sought forgetfulness of the Scorpion problem--and of the dark eyes of Mlle. Dorian. He was not entirely successful, and returning by a different route he lost himself in memories which were sweetly mournful. A taxicab passed him, moving slowly very close to the pavement. He scarcely noted it until it had proceeded some distance ahead of him. Then its slow progress so near to the pavement at last attracted his attention, and he stared vacantly towards the closed vehicle. Mlle. Dorian was leaning out of the window and looking back at him! Stuart's heart leapt high. For an instant he paused, then began to walk rapidly after the retreating vehicle. Perceiving that she had attracted his attention, the girl extended a white-gloved hand from the window and dropped a note upon the edge of the pavement. Immediately she withdrew into the vehicle--which moved away at accelerated speed, swung around the next corner and was gone. Stuart ran forward and picked up the note. Without pausing to read it, he pressed on to the corner. The cab was already two hundred yards away, and he recognized pursuit to be out of the question. The streets were almost deserted at the moment, and no one apparently had witnessed the episode. He unfolded the sheet of plain note-paper, faintly perfumed with jasmine, and read the following, written in an uneven feminine hand: "Close your shutters at night. Do not think too bad of me." CHAPTER XI THE BLUE RAY Dusk found Stuart in a singular frame of mind. He was torn between duty--or what he conceived to be his duty--to the community, and ... something else. A messenger from New Scotland Yard had brought him a bundle of documents relating to the case of Sir Frank Narcombe, and a smaller packet touching upon the sudden end of Henrik Ericksen, the Norwegian electrician, and the equally unexpected death of the Grand Duke Ivan. There were medical certificates, proceedings of coroners, reports of detectives, evidence of specialists and statements of friends, relatives and servants of the deceased. A proper examination of all the documents represented many hours of close study.