"Certainly, Inspector."

From the waiting-room they went up a short flight of stairs into the small apartment in which Stuart saw his patients. Dunbar looked slowly about him, standing in the middle of the room, then crossed and stared out of the window into the narrow lane below.

"Where were you when he gave you the envelope?" he snapped suddenly.

"At the table," replied Stuart with surprise.

"Was the table-lamp alight?"

"Yes. I always light it when seeing patients."

"Did you take the letter into the study to seal it in the other envelope?"

"I did, and he came along and witnessed me do it."

"Ah," said Dunbar, and scribbled busily in his note-book. "We are badly tied at Scotland Yard, doctor, and this case looks like being another for which somebody else will reap the credit. I am going to make a request that will surprise you."

He tore a leaf out of the book and folded it carefully.

"I am going to ask you to seal up something and lock it away! But I don't think you'll be troubled by cowled burglars or beautiful women because of it. On this piece of paper I have written--_a"_--he ticked off the points on his fingers: "what I believe to be the name of the man who cut out the cardboard and sealed it in an envelope; _b_: the name of the cabman; and, _c_: the name of the man who rang me up here last night and gave me information which had only just reached the Commissioner. I'll ask you to lock it away until it's wanted, doctor."

"Certainly, if you wish it," replied Stuart. "Come into the study and you shall see me do as you direct. I may add that the object to be served is not apparent to me."

Entering the study, he took an envelope, enclosed the piece of paper, sealed the lapel and locked the envelope in the same drawer of the bureau which once had contained that marked 30.

"Mlle. Dorian has a duplicate key to this drawer." he said. "Are you prepared to take the chance?"

"Quite," replied Dunbar, smiling; "although my information is worth more than that which she risked so much to steal."

"It's most astounding. At every step the darkness increases. Why should _anyone_ have asked me to lock up a blank piece of cardboard?"

"Why, indeed," murmured Dunbar. "Well, I may as well get back. I am expecting a report from Sowerby. Look after yourself, sir. I'm inclined to think your pretty patient was talking square when she told you there might be danger."

Stuart met the glance of the tawny eyes.

"What d'you mean, Inspector? Why should _I_ be in danger?"

"Because," replied Inspector Dunbar, "if 'The Scorpion' is a poisoner, as the chief seems to think, there's really only one man in England he has to fear, and that man is Dr. Keppel Stuart."

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 gra.s.s, 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 inst.i.tution 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 pa.s.sed 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 doc.u.ments 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 doc.u.ments represented many hours of close study.

Stuart was flattered by the opinion held of his ability by the a.s.sistant Commissioner, but dubious of his chance of detecting any flaw in the evidence which had escaped the scrutiny of so many highly trained observers.

He paced the study restlessly. Although more than six hours had elapsed, he had not communicated to Scotland Yard the fact of his having seen Mlle. Dorian that afternoon. A hundred times he had read the message, although he knew it by heart, knew the form of every letter, the odd crossing of the _t'_s and the splashy dotting of the _i_'s.

If only he could have taken counsel with someone--with someone not bound to act upon such information--it would have relieved his mental stress. His ideas were so chaotic that he felt himself to be incapable of approaching the task presented by the pile of papers lying upon his table.

The night was pleasantly warm and the sky cloudless. Often enough he found himself glancing toward the opened French windows, and once he had peered closely across into the belt of shadow below the hedge, thinking that he had detected something which moved there. Stepping to the window, the slinking shape had emerged into the moonlight--and had proclaimed itself to be that of a black cat!

Yet he had been sorely tempted to act upon the advice so strangely offered. He refrained from doing so, however, reflecting that to spend his evenings with closed and barred shutters now that a spell of hot weather seemed to be imminent would be insufferable. Up and down the room he paced tirelessly, always confronted by the eternal problem.

Forcing himself at last to begin work if only as a sedative, he filled and lighted his pipe, turned off the centre lamp and lighted the reading lamp upon his table. He sat down to consider the papers bearing upon the death of Eriksen. For half an hour he read on steadily and made a number of pencil notes. Then he desisted and sat staring straight before him.

What possible motive could there be in a.s.sa.s.sinating these people? The case of the Grand Duke might be susceptible of explanation, but those of Henrik Ericksen and Sir Frank Narcombe were not. Furthermore he could perceive no links connecting the three, and no reason why they should have engaged the attention of a common enemy. Such crimes would seem to be purposeless. a.s.suming that "The Scorpion" was an individual, that individual apparently was a dangerous homicidal maniac.

But, throughout the doc.u.ments, he could discover no clue pointing to the existence of such an ent.i.ty. "The Scorpion" might be an invention of the fertile brain of M. Gaston Max; for it had become more and more evident, as he had read, that the attempt to trace these deaths to an identical source had originated at the Service de Surete, and it was from Paris that the name "The Scorpion" had come. The fate of Max was significant, of course. The chances of his death proving to have been due to accident were almost negligible and the fact that a fragment of a golden scorpion had actually been found upon his body was certainly curious.

"Close your shutters at night...."

How the words haunted him and how hotly he despised himself for a growing apprehension which refused to be ignored. It was more mental than physical, this dread which grew with the approach of midnight, and it resembled that which had robbed him of individuality and all but stricken him inert when he had seen upon the moon-bright screen of the curtains the shadow of a cowled man.

Dark forces seemed to be stirring, and some unseen menace crept near to him out of the darkness.

The house was of early Victorian fashion and ma.s.sive folding shutters were provided to close the French windows. He never used them, as a matter of fact, but now he tested the fastenings which kept them in place against the inner wall and even moved them in order to learn if they were still serviceable.

Of all the mysteries which baffled him, that of the piece of cardboard in the envelope sealed with a Chinese coin was the most irritating. It seemed like the purposeless trick of a child, yet it had led to the presence of the cowled man--and to the presence of Mlle. Dorian. Why?

He sat down at his table again.

"d.a.m.n the whole business!" he said. "It is sending me crazy."