“Possibly not, my good Watson. It may surprise you to know that the man upon earth who is best versed in this disease is not a medical man, but a planter. Mr. Culverton Smith is a well-known resident of Sumatra, now visiting London. An outbreak of the disease upon his plantation, which was distant from medical aid, caused him to study it himself, with some rather far-reaching consequences. He is a very methodical person, and I did not desire you to start before six, because I was well aware that you would not find him in his study. If you could persuade him to come here and give us the benefit of his unique experience of this disease, the investigation of which has been his dearest hobby, I cannot doubt that he could help me.”