“There was one other thing I wish to tell you, Mr. Holmes. I have the address of the man in London to whom the professor writes. He seems to have written this morning, and I got it from his blotting-paper. It is an ignoble position for a trusted secretary, but what else can I do?”

Holmes glanced at the paper and put it into his pocket.

“Dorak - a curious name. Slavonic, I imagine. Well, it is an important link in the chain. We return to London this afternoon, Mr. Bennett. I see no good purpose to be served by our remaining. We cannot arrest the professor because he has done no crime, nor can we place him under constraint, for he cannot be proved to be mad. No action is as yet possible.”

“Then what on earth are we to do?”

“A little patience, Mr. Bennett. Things will soon develop. Unless I am mistaken, next Tuesday may mark a crisis. Certainly we shall be in Camford on that day. Meanwhile, the general position is undeniably unpleasant, and if Miss Presbury can prolong her visit- -”

“That is easy.”

“Then let her stay till we can assure her that all danger is past. Meanwhile, let him have his way and do not cross him. So long as he is in a good humour all is well.”

“There he is!” said Bennett in a startled whisper. Looking between the branches we saw the tall, erect figure emerge from the hall door and look around him. He stood leaning forward, his hands swinging straight before him, his head turning from side to side. The secretary with a last wave slipped off among the trees, and we saw him presently rejoin his employer, the two entering the house together in what seemed to be animated and even excited conversation.

“I expect the old gentleman has been putting two and two together,” said Holmes as we walked hotelward. “He struck me as having a particularly clear and logical brain from the little I saw of him. Explosive, no doubt, but then from his point of view he has something to explode about if detectives are put on his track and he suspects his own household of doing it. I rather fancy that friend Bennett is in for an uncomfortable time.”

Holmes stopped at a post-office and sent off a telegram on our way. The answer reached us in the evening, and he tossed it across to me.

Have visited the Commercial Road and seen Dorak. Suave person, Bohemian, elderly. Keeps large general store.

MERCER.

“Mercer is since your time,” said Holmes. “He is my general utility man who looks up routine business. It was important to know something of the man with whom our professor was so secretly corresponding. His nationality connects up with the Prague visit.”

“Thank goodness that something connects with something,” said I. “At present we seem to be faced by a long series of inexplicable incidents with no bearing upon each other. For example, what possible connection can there be between an angry wolfhound and a visit to Bohemia, or either of them with a man crawling down a passage at night? As to your dates, that is the biggest mystification of all.”

Holmes smiled and rubbed his hands. We were, I may say, seated in the old sitting-room of the ancient hotel, with a bottle of the famous vintage of which Holmes had spoken on the table between us.

“Well, now, let us take the dates first,” said he, his finger-tips together and his manner as if he were addressing a class. “This excellent young man’s diary shows that there was trouble upon July 2d, and from then onward it seems to have been at nine-day intervals, with, so far as I remember, only one exception. Thus the last outbreak upon Friday was on September 3d, which also falls into the series, as did August 26th, which preceded it. The thing is beyond coincidence.”

I was forced to agree.