I had never seen my friend’s face so grim or his brow so dark as it was when we turned from the scene of this investigation. We had walked several times up and down the lawn, neither Miss Stoner nor myself liking to break in upon his thoughts before he roused himself from his reverie.

“It is very essential, Miss Stoner,” said he, “that you should absolutely follow my advice in every respect.”

“I shall most certainly do so.”

“The matter is too serious for any hesitation. Your life may depend upon your compliance.”

“I assure you that I am in your hands.”

“In the first place, both my friend and I must spend the night in your room.”

Both Miss Stoner and I gazed at him in astonishment.

“Yes, it must be so. Let me explain. I believe that that is the village inn over there?”

“Yes, that is the Crown.”

“Very good. Your windows would be visible from there?”

“Certainly.”

“You must confine yourself to your room, on pretence of a headache, when your stepfather comes back. Then when you hear him retire for the night, you must open the shutters of your window, undo the hasp, put your lamp there as a signal to us, and then withdraw quietly with everything which you are likely to want into the room which you used to occupy. I have no doubt that, in spite of the repairs, you could manage there for one night.”

“Oh, yes, easily.”

“The rest you will leave in our hands.”

“But what will you do?”

“We shall spend the night in your room, and we shall investigate the cause of this noise which has disturbed you.”

“I believe, Mr. Holmes, that you have already made up your mind,” said Miss Stoner, laying her hand upon my companion’s sleeve.

“Perhaps I have.”

“Then, for pity’s sake, tell me what was the cause of my sister’s death.”

“I should prefer to have clearer proofs before I speak.”

“You can at least tell me whether my own thought is correct, and if she died from some sudden fright.”

“No, I do not think so. I think that there was probably some more tangible cause. And now, Miss Stoner, we must leave you, for if Dr. Roylott returned and saw us our journey would be in vain. Good-bye, and be brave, for if you will do what I have told you you may rest assured that we shall soon drive away the dangers that threaten you.”

Sherlock Holmes and I had no difficulty in engaging a bedroom and sitting-room at the Crown Inn. They were on the upper floor, and from our window we could command a view of the avenue gate, and of the inhabited wing of Stoke Moran Manor House. At dusk we saw Dr. Grimesby Roylott drive past, his huge form looming up beside the little figure of the lad who drove him. The boy had some slight difficulty in undoing the heavy iron gates, and we heard the hoarse roar of the doctor’s voice and saw the fury with which he shook his clinched fists at him. The trap drove on, and a few minutes later we saw a sudden light spring up among the trees as the lamp was lit in one of the sitting-rooms.

“Do you know, Watson,” said Holmes as we sat together in the gathering darkness, “I have really some scruples as to taking you to-night. There is a distinct element of danger.”

“Can I be of assistance?”

“Your presence might be invaluable.”

“Then I shall certainly come.”

“It is very kind of you.”

“You speak of danger. You have evidently seen more in these rooms than was visible to me.”

“No, but I fancy that I may have deduced a little more. I imagine that you saw all that I did.”

“I saw nothing remarkable save the bell-rope, and what purpose that could answer I confess is more than I can imagine.”

“You saw the ventilator, too?”

“Yes, but I do not think that it is such a very unusual thing to have a small opening between two rooms. It was so small that a rat could hardly pass through.”

“I knew that we should find a ventilator before ever we came to Stoke Moran.”

“My dear Holmes!”

“Oh, yes, I did. You remember in her statement she said that her sister could smell Dr. Roylott’s cigar. Now, of course that suggested at once that there must be a communication between the two rooms. It could only be a small one, or it would have been remarked upon at the coroner’s inquiry. I deduced a ventilator.”

“But what harm can there be in that?”

“Well, there is at least a curious coincidence of dates. A ventilator is made, a cord is hung, and a lady who sleeps in the bed dies. Does not that strike you?”

“I cannot as yet see any connection.”

“Did you observe anything very peculiar about that bed?”

“No.”

“It was clamped to the floor. Did you ever see a bed fastened like that before?”

“I cannot say that I have.”

“The lady could not move her bed. It must always be in the same relative position to the ventilator and to the rope – or so we may call it, since it was clearly never meant for a bell-pull.”

“Holmes,” I cried, “I seem to see dimly what you are hinting at. We are only just in time to prevent some subtle and horrible crime.”

“Subtle enough and horrible enough. When a doctor does go wrong he is the first of criminals. He has nerve and he has knowledge. Palmer[73] and Pritchard[74] were among the heads of their profession. This man strikes even deeper, but I think, Watson, that we shall be able to strike deeper still. But we shall have horrors enough before the night is over; for goodness’ sake let us have a quiet pipe and turn our minds for a few hours to something more cheerful.”

About nine o’clock the light among the trees was extinguished, and all was dark in the direction of the Manor House. Two hours passed slowly away, and then, suddenly, just at the stroke of eleven, a single bright light shone out right in front of us.

“That is our signal,” said Holmes, springing to his feet; “it comes from the middle window.”

As we passed out he exchanged a few words with the landlord, explaining that we were going on a late visit to an acquaintance, and that it was possible that we might spend the night there. A moment later we were out on the dark road, a chill wind blowing in our faces, and one yellow light twinkling in front of us through the gloom to guide us on our sombre errand.

There was little difficulty in entering the grounds, for unrepaired breaches gaped in the old park wall. Making our way among the trees, we reached the lawn, crossed it, and were about to enter through the window when out from a clump of laurel bushes there darted what seemed to be a hideous and distorted child, who threw itself upon the grass with writhing limbs and then ran swiftly across the lawn into the darkness.

“My God!” I whispered; “did you see it?”

Holmes was for the moment as startled as I. His hand closed like a vise upon my wrist in his agitation. Then he broke into a low laugh and put his lips to my ear.

“It is a nice household,” he murmured. “That is the baboon.”

I had forgotten the strange pets which the doctor affected. There was a cheetah, too; perhaps we might find it upon our shoulders at any moment. I confess that I felt easier in my mind when, after following Holmes’s example and slipping off my shoes, I found myself inside the bedroom. My companion noiselessly closed the shutters, moved the lamp onto the table, and cast his eyes round the room. All was as we had seen it in the daytime. Then creeping up to me and making a trumpet of his hand, he whispered into my ear again so gently that it was all that I could do to distinguish the words:

“The least sound would be fatal to our plans.”

I nodded to show that I had heard.

“We must sit without light. He would see it through the ventilator.”

I nodded again.