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"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?"