“That was the state of things, Watson, when upon the Tuesday morning I, at the request of Major Murphy, went down to Aldershot to supplement the efforts of the police. I think that you will acknowledge that the problem was already one of interest, but my observations soon made me realize that it was in truth much more extraordinary than would at first sight appear.

“Before examining the room I cross-questioned the servants, but only succeeded in eliciting the facts which I have already stated. One other detail of interest was remembered by Jane Stewart, the housemaid. You will remember that on hearing the sound of the quarrel she descended and returned with the other servants. On that first occasion, when she was alone, she says that the voices of her master and mistress were sunk so low that she could hardly hear anything, and judged by their tones rather than their words that they had fallen out. On my pressing her, however, she remembered that she heard the word David uttered twice by the lady. The point is of the utmost importance as guiding us towards the reason of the sudden quarrel. The colonel’s name, you remember, was James.

“There was one thing in the case which had made the deepest impression both upon the servants and the police. This was the contortion of the colonel’s face. It had set, according to their account, into the most dreadful expression of fear and horror which a human countenance is capable of assuming. More than one person fainted at the mere sight of him, so terrible was the effect. It was quite certain that he had foreseen his fate, and that it had caused him the utmost horror. This, of course, fitted in well enough with the police theory, if the colonel could have seen his wife making a murderous attack upon him. Nor was the fact of the wound being on the back of his head a fatal objection to this, as he might have turned to avoid the blow. No information could be got from the lady herself, who was temporarily insane from an acute attack of brain-fever.

“From the police I learned that Miss Morrison, who you remember went out that evening with Mrs. Barclay, denied having any knowledge of what it was which had caused the ill-humour in which her companion had returned.

“Having gathered these facts, Watson, I smoked several pipes over them, trying to separate those which were crucial from others which were merely incidental. There could be no question that the most distinctive and suggestive point in the case was the singular disappearance of the door-key. A most careful search had failed to discover it in the room. Therefore it must have been taken from it. But neither the colonel nor the colonel’s wife could have taken it. That was perfectly clear. Therefore a third person must have entered the room. And that third person could only have come in through the window. It seemed to me that a careful examination of the room and the lawn might possibly reveal some traces of this mysterious individual. You know my methods, Watson. There was not one of them which I did not apply to the inquiry. And it ended by my discovering traces, but very different ones from those which I had expected. There had been a man in the room, and he had crossed the lawn coming from the road. I was able to obtain five very clear impressions of his footmarks: one in the roadway itself, at the point where he had climbed the low wall, two on the lawn, and two very faint ones upon the stained boards near the window where he had entered. He had apparently rushed across the lawn, for his toe-marks were much deeper than his heels. But it was not the man who surprised me. It was his companion.”

“His companion!”

Holmes pulled a large sheet of tissue-paper out of his pocket and carefully unfolded it upon his knee.

“What do you make of that?” he asked.