“The practical application of what I have said is very close to the problem which I am investigating. It is a tangled skein, you understand, and I am looking for a loose end. One possible loose end lies in the question: Why does Professor Presbury’s wolfhound, Roy, endeavour to bite him?”

I sank back in my chair in some disappointment. Was it for so trivial a question as this that I had been summoned from my work? Holmes glanced across at me.

“The same old Watson!” said he. “You never learn that the gravest issues may depend upon the smallest things. But is it not on the face of it strange that a staid, elderly philosopher⁠—you’ve heard of Presbury, of course, the famous Camford physiologist?⁠—that such a man, whose friend has been his devoted wolfhound, should now have been twice attacked by his own dog? What do you make of it?”

“The dog is ill.”