"Scotland Yard man," interrupted Dan, nodding several times. "He came to see Sir Charles on business and found the corpse." "Just so. Well, after dinner we had a chat, and he told me that he was anxious to learn who killed Moon, because he didn't want any more murders of the kind to happen--as a police official, you understand."
"Strange he should be confidential on that point," murmured Halliday thoughtfully, "seeing that he wished his theory regarding a possible gang kept quiet, in the hope of making discoveries."
"He has changed his mind about secrecy, and so has Tenson," said Freddy. "Oh!" Dan raised his eyebrows. "The Inspector. You have seen him also?" Laurance nodded. "After I saw Durwin, and learned what he had to say I saw Tenson, and interviewed him. They told me about the fly on the neck, and remembering the case of the purple fern, and having regard to the fact that the fly in question was artificial, both men are inclined to believe in the existence of a gang, whose trade-mark the said fly is." Dan nodded again. "Quite so; and then Durwin came to see Moon and hear about the gang. He found him dead."
"So you said; so Durwin said," rejoined Laurance quietly. "It seems very certain, putting this and that together, that Sir Charles became dangerous to this gang, whatever it is, and wherever it exists, so was put to death by the false Mrs. Brown, who came expressly to kill him."
"So far I am with you on all fours," said Halliday. "Well?"
"Well, both Durwin and Tenson, dreading lest the gang may commit another crime, wish me to make the matter as public as I can, so as to frighten the beasts."
"H'm!" said Dan, looking at his neat brown boots. "They have changed their minds, it seems. Their first idea was to keep the matter quiet, so as to catch these devils red-handed. However, publicity may be a good thing. How do you intend to begin?"
"I have got facts from Tenson and from Durwin," said Freddy promptly; "and now, since you saw the body and found the fly, I want to get the facts from you. On what I acquire I shall write a letter in that extra sheet of ours, and you can be pretty certain from what you know of human nature that any amount of people will reply to my letter."
"They may reply to no purpose."
"I'm not so sure of that, Dan. If I mention the fly as a trade-mark and recall the strange case of the purple fern, some one may write about matters known to themselves from positive knowledge. If this gang exists, it has committed more murders than one, but the fly being a small insect may not have been noticed as a trade-mark in the other crimes. I wonder you spotted it anyhow."