"Why didn't you go straight home and get it?" inquired Freddy anxiously, for there was no denying that Dan looked considerably fagged. "I read about this death of Durwin in a late edition of an evening paper, and couldn't rest until I knew the truth. The paper only gave a hint. Tell me what you know." Laurance did so, and then handed Halliday a proof of his article on the subject which was to appear in the morning issue of _The Moment_. He supplemented the same with further information. "I went down to see if there was any scent on the clothes of the corpse," he explained, "it's still at Blackheath, you know, in charge of the Inspector. There's no perfume, anyhow." "And no fly?" "No. I asked that the moment I saw Durwin stretched out on the ground. If this crime is the work of the gang, the sign-manual is absent." "All the same it is the work of the gang, I truly believe," remarked Dan in grim tones. "Durwin has been on the hunt, and very probably, since he discovered the death of Moon first of all, he has been watched. One of the gang got behind him in the crowd, and knifed him in the crush. It would be perfectly easy for the assassin to slip away, without being noticed, since every one was watching the flight of the aeroplanes." Laurance nodded. "I agree with you. But who is the assassin?" "Well," said Dan reflectively, "I saw Penn on the ground." "The deuce you did," cried Freddy jumping up, "did he----" "Don't be in too great a hurry. He seems to me much too nervous a man to handle this job." "But he belongs to the gang," insisted Laurance sharply. "He has as good as admitted that much by what he said of the perfume." "Oh, yes, I believe he has something to do with the association, which, by the way, appears to be a kind of joint-stock company, like that one mentioned by Balzac in his story 'Histoire des Treize,' and----" "Oh, hang your literary references," interrupted Freddy, anxiously pacing the office, "do you believe that Penn struck the blow?" "No, I don't. The gang must have better men than he to strike." "Or women," muttered Laurance, thinking of the false Mrs. Brown. "However, since Penn was in the crowd, and is plainly in the secret of the gang, don't you think we ought to tell the Blackheath Inspector about the matter, and also Inspector Tenson, who had charge of the Hampstead crime?" "No," said Dan, after a pause. "If Penn is arrested and questioned, he will say nothing. As he hinted, he would be killed if he gave away the gang; so as he wouldn't split, when I threatened him on the aeroplane, he certainly won't speak out if questioned by the police. And we haven't got enough evidence to prove his complicity, remember. Better keep silence, Freddy, and let the police fog out this crime alone. Meanwhile, we can look round and keep an eye on Penn."