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." "It was easily seen, being on the back of the neck near the wound. Besides, flies in November--the month of the murder--are rare. Finally Tenson discovered the fly to be artificial, which shows that it was purposely placed on the dead man's neck, near the wound. H'm!" he reflected, "perhaps someone may know of some crime with the fly trade-mark, and in that case we can be certain that such a gang does exist." "So I think," cried Laurance quickly, "and for that reason I intend to start a discussion by writing an open letter. Publicity may frighten the beasts into dropping their trade; on the other hand, it may goad the gang into asserting itself. In either case the subject will be ventilated, and we may learn more or less of the truth."