Holmes greets Watson, then explains how he knew his friend was inside the hut. Watson dropped his cigarette before entering; it is a distinctive brand. He asks how Watson found the hut; Watson says the delivery boy gave it away. Holmes says the boy is Cartwright from London, who also has done some useful spying.

Holmes confesses that he wanted to study the case from nearby without giving away his presence, and were Watson to know of it, he might try to visit with news and risk giving the game away. Watson feel hurt by the deception and from the use of Cartwright as Holmes’s informant. Holmes pulls from his pocket Watson’s well-thumbed reports and declares them invaluable. This mollifies the doctor.

Watson updates Holmes on his interview with Laura Lyons. Holmes says the information fills in an important gap in the mystery. He tells Watson that Lyons is close to Stapleton, and that Beryl isn’t his sister but his wife. Holmes followed up on Watson’s reports to locate the school Stapleton had presided over. Holmes also learned that Stapleton and Beryl were identified as an entomologist and his wife, and that they had disappeared after a school calamity.