“My dear Holmes,” I exclaimed, “how on earth- -”

“Well, well, you may see for yourself. If not, there’s no harm done. Of course, we always have the optician clue to fall back upon, but I take a short cut when I can get it. Ah, here is the good Mrs. Marker! Let us enjoy five minutes of instructive conversation with her.”

I may have remarked before that Holmes had, when he liked, a peculiarly ingratiating way with women, and that he very readily established terms of confidence with them. In half the time which he had named, he had captured the housekeeper’s goodwill and was chatting with her as if he had known her for years.

“Yes, Mr. Holmes, it is as you say, sir. He does smoke something terrible. All day and sometimes all night, sir. I’ve seen that room of a morning - well, sir, you’d have thought it was a London fog. Poor young Mr. Smith, he was a smoker also, but not as bad as the professor. His health - well, I don’t know that it’s better nor worse for the smoking.”

“Ah!” said Holmes, “but it kills the appetite.”

“Well, I don’t know about that, sir.”

“I suppose the professor eats hardly anything?”

“Well, he is variable. I’ll say that for him.”

“I’ll wager he took no breakfast this morning, and won’t face his lunch after all the cigarettes I saw him consume.”

“Well, you’re out there, sir, as it happens, for he ate a remarkable big breakfast this morning. I don’t know when I’ve known him make a better one, and he’s ordered a good dish of cutlets for his lunch. I’m surprised myself, for since I came into that room yesterday and saw young Mr. Smith lying there on the floor, I couldn’t bear to look at food. Well, it takes all sorts to make a world, and the professor hasn’t let it take his appetite away.”

We loitered the morning away in the garden. Stanley Hopkins had gone down to the village to look into some rumours of a strange woman who had been seen by some children on the Chatham Road the previous morning. As to my friend, all his usual energy seemed to have deserted him. I had never known him handle a case in such a half-hearted fashion. Even the news brought back by Hopkins that he had found the children, and that they had undoubtedly seen a woman exactly corresponding with Holmes’s description, and wearing either spectacles or eyeglasses, failed to rouse any sign of keen interest. He was more attentive when Susan, who waited upon us at lunch, volunteered the information that she believed Mr. Smith had been out for a walk yesterday morning, and that he had only returned half an hour before the tragedy occurred. I could not myself see the bearing of this incident, but I clearly perceived that Holmes was weaving it into the general scheme which he had formed in his brain. Suddenly he sprang from his chair and glanced at his watch. “Two o’clock, gentlemen,” said he. “We must go up and have it out with our friend, the professor.”

The old man had just finished his lunch, and certainly his empty dish bore evidence to the good appetite with which his housekeeper had credited him. He was, indeed, a weird figure as he turned his white mane and his glowing eyes towards us. The eternal cigarette smouldered in his mouth. He had been dressed and was seated in an armchair by the fire.

“Well, Mr. Holmes, have you solved this mystery yet?” He shoved the large tin of cigarettes which stood on a table beside him towards my companion. Holmes stretched out his hand at the same moment, and between them they tipped the box over the edge. For a minute or two we were all on our knees retrieving stray cigarettes from impossible places. When we rose again, I observed Holmes’s eyes were shining and his cheeks tinged with colour. Only at a crisis have I seen those battle-signals flying.

“Yes,” said he, “I have solved it.”