"And you connect this attack with your lodger?" "Well, we've lived there fifteen years and no such happenings ever came before. I've had enough of him. Money's not everything. I'll have him out of my house before the day is done." "Wait a bit, Mrs. Warren. Do nothing rash. I begin to think that this affair may be very much more important than appeared at first sight. It is clear now that some danger is threatening your lodger. It is equally clear that his enemies, lying in wait for him near your door, mistook your husband for him in the foggy morning light. On discovering their mistake they released him. What they would have done had it not been a mistake, we can only conjecture."

"Well, what am I to do, Mr. Holmes?" "I have a great fancy to see this lodger of yours, Mrs. Warren."

"I don't see how that is to be managed, unless you break in the door. I always hear him unlock it as I go down the stair after I leave the tray."

"He has to take the tray in. Surely we could conceal ourselves and see him do it."

The landlady thought for a moment.

"Well, sir, there's the box-room opposite. I could arrange a looking-glass, maybe, and if you were behind the door —" "Excellent!" said Holmes. "When does he lunch?"

"About one, sir."

"Then Dr. Watson and I will come round in time. For the present, Mrs. Warren, good-bye."

At half-past twelve we found ourselves upon the steps of Mrs. Warren's house – a high, thin, yellow brick edifice in Great Orme Street, a narrow thoroughfare at the northeast side of the British Museum. Standing as it does near the corner of the street it commands a view down Howe Street, with its more pretentious houses. Holmes pointed with a chuckle to one of these, a row of residential flats, which projected so that they could not fail to catch the eye.

"See, Watson!" said he. " 'High red house with stone facings.' There is the signal station all right. We know the place, and we know the code; so surely our task should be simple. There's a 'to let' card in that window. It is evidently an empty flat to which the confederate has access. Well, Mrs. Warren, what now?"

"I have it all ready for you. If you will both come up and leave your boots below on the landing, I'll put you there now."

It was an excellent hiding place which she had arranged. The mirror was so placed that, seated in the dark, we could very plainly see the door opposite. We had hardly settled down in it, and Mrs. Warren left us, when a distant tinkle announced that our mysterious neighbor had rung. Presently the landlady appeared with the tray, laid it down upon a chair beside the closed door, and then, treading heavily, departed. Crouching together in the angle of the door, we kept our eyes fixed upon the mirror. Suddenly, as the landlady's footsteps died away, there was the creak of a turning key, the handle revolved, and two thin hands darted out and lifted the tray from the chair. An instant later it was hurriedly replaced, and I caught a glimpse of a dark, beautiful, horrified face glaring at the narrow opening of the box-room. Then the door crashed to, the key turned once more, and all was silence. Holmes twitched my sleeve, and together we stole down the stair.

"I will call again in the evening," said he to the expectant landlady. "I think, Watson, we can discuss this business better in our own quarters."

"My surmise, as you saw, proved to be correct," said he, speaking from the depths of his easy-chair. "There has been a substitution of lodgers. What I did not foresee is that we should find a woman, and no ordinary woman, Watson."

"She saw us."

"Well, she saw something to alarm her. That is certain. The general sequence of events is pretty clear, is it not? A couple seek refuge in London from a very terrible and instant danger. The measure of that danger is the rigor of their precautions. The man, who has some work which he must do, desires to leave the woman in absolute safety while he does it. It is not an easy problem, but he solved it in an original fashion, and so effectively that her presence was not even known to the landlady who supplies her with food. The printed messages, as is now evident, were to prevent her sex being discovered by her writing. The man cannot come near the woman, or he will guide their enemies to her. Since he cannot communicate with her direct, he has recourse to the agony column of a paper. So far all is clear."

"But what is at the root of it?"

"Ah, yes, Watson – severely practical, as usual! What is at the root of it all? Mrs. Warren's whimsical problem enlarges somewhat and assumes a more sinister aspect as we proceed. This much we can say: that it is no ordinary love escapade. You saw the woman's face at the sign of danger. We have heard, too, of the attack upon the landlord, which was undoubtedly meant for the lodger. These alarms, and the desperate need for secrecy, argue that the matter is one of life or death. The attack upon Mr. Warren further shows that the enemy, whoever they are, are themselves not aware of the substitution of the female lodger for the male. It is very curious and complex, Watson."

"Why should you go further in it? What have you to gain from it?"

"What, indeed? It is art for art's sake, Watson. I suppose when you doctored you found yourself studying cases without though{ of a fee?"

"For my education, Holmes."

"Education never ends, Watson. It is a series of lessons with the greatest for the last. This is an instructive case. There is neither money nor credit in it, and yet one would wish to tidy it up. When dusk comes we should find ourselves one stage advanced in our investigation."

When we returned to Mrs. Warren's rooms, the gloom of a London winter evening had thickened into one gray curtain, a dead monotone of color, broken only by the sharp yellow squares of the windows and the blurred haloes of the gas-lamps. As we peered from the darkened sitting-room of the lodging– house, one more dim light glimmered high up through the obscurity.

"Someone is moving in that room," said Holmes in a whisper, his gaunt and eager face thrust forward to the windowpane. "Yes, I can see his shadow. There he is again! He has a candle in his hand. Now he is peering across. He wants to be sure that she is on the lookout. Now he begins to flash. Take the message also, Watson, that we may check each other. A single flash – that is A, surely. Now, then. How many did you make it? Twenty. So did I. That should mean T. AT – that's intelligible enough! Another T. Surely this is the beginning of a second word. Now, then – TENTA. Dead stop. That can't be all, Watson? ATTENTA gives no sense. Nor is it any better as three words AT, TEN, TA, unless T. A. are a person's initials. There it goes again! What's that? ATTE why, it is the same message over again. Curious, Watson, very curious! Now he is off once more! AT – why, he is repeating it for the third time. ATTENTA three times! How often will he repeat it? No, that seems to be the finish. He has withdrawn from the window. What do you make of it, Watson?"

"A cipher message, Holmes."

My companion gave a sudden chuckle of comprehension.

"And not a very obscure cipher, Watson," said he. "Why, of course, it is Italian! The A means that it is addressed to a woman. 'Beware! Beware! Beware!' How's that, Watson?"

"I believe you have hit it."

"Not a doubt of it. It is a very urgent message, thrice repeated to make it more so. But beware of what? Wait a bit; he is coming to the window once more."