The secretary of the late Sir Charles Moon smiled irresolutely when he recognised Dan. That young gentleman, who thought Penn a weak-kneed idiot, had never taken much notice of him, and but for the fact that he was perfumed with the unusual scent would not have spoken to him now. But as he looked at the lank creature with his yellow face, and scanty moustache, he guessed that he was exactly the effeminate sort of person who would use perfume. What he wished to know was why he affected this particular kind of fragrance, and whence he obtained it. To gain the information he pretended a friendliness for the man he was far from feeling. Dan, strong, virile, and self-confident, was not altogether just to Penn, who was not responsible for his pallid looks and weak character. But Halliday was not a perfect individual by any means, and had yet to learn that the weak are meant to be protected and helped instead of being despised.

“You here, Mr. Penn?” said Dan, thus formal to mark the difference between them.

“Yes,” replied the man in his faint, hesitating voice, and, as they moved out of the crowd, Halliday smelt the weird perfume more strongly than ever shaken from Penn’s clothes by his movements. “I stopped to look at the accident.”

“A very ordinary one,” rejoined Halliday, with a shrug. “By the way, I have not seen you since the funeral of Sir Charles. What are you doing now, if I may ask?”

“I am secretary to Lord Curberry.”

“Oh!” The reply gave Dan something of a shock, for he did not expect at the moment to hear his rival’s name. But then the whole incident of meeting Penn and smelling the incriminating perfume was strange. Monsieur Chance had proved himself to be an actuality instead of the mythical personage Dan had believed him to be. It was certainly odd that the meeting had taken place, and odder still that Penn should prove to be the servant of Curberry.

As Halliday said nothing more than “Oh!” the other man stroked his moustache and explained. “Sir John got me the post, Mr. Halliday,” he said with his shifty eyes anywhere but on Dan’s inquiring face. “I was quite stranded after Sir Charles’s unexpected death, and did not know where to turn for employment. As I support a widowed mother, the situation was rather serious, so I took my courage in my hands and went to Sir John. He was good enough to recommend me to Lord Curberry, and I have been with his lordship for a month, more or less.”

“I congratulate you, Mr. Penn, and Lord Curberry also. Sir Charles always said you were an excellent secretary.” Dan stopped as Penn bowed his acknowledgements to the compliment, and cast a keen side glance at the man. They were walking through Trafalgar Square by this time; passing under the shadow of Nelson’s Column. “Do you know what I was thinking of when behind you in the crowd yonder, Mr. Penn?” he asked abruptly, and it must be confessed rather undiplomatically, if he wished to get at the truth.

“No,” said the secretary, with simplicity and manifest surprise. “No, Mr. Halliday, how can I guess your thoughts?”

“I was thinking of the murder of your late employer,” said Dan straightly.

Penn blinked and shivered. “It’s a horrible subject to think about,” he remarked in a low voice. “I can scarcely get it out of my own thoughts. I suppose the sight of me reminded you of the crime, Mr. Halliday?”

“Scarcely, since I was behind you and did not recognise you until you turned,” replied Dan, calmly, and the other appeared to be surprised.

“Then how —” he began, only to be cut short.

“It’s that scent.”

“Scent!” echoed Penn nervously but manifestly still surprised. “I don’t understand what you mean, Mr. Halliday. I like scent, and use much of it.”

Dan’s lip curled. “So I perceive. But where did you get the particular scent you are using now, may I ask?”

Something in his tone annoyed the secretary, for he drew himself up and halted. “I don’t know why you should criticise my tastes, Mr. Halliday.”

“I’m not criticising them, and don’t jump down my throat. But you reek of some strange perfume, which I last smelt —” He paused.

“You cannot have smelt it anywhere,” said Penn indifferently.

“What do you mean by that exactly?” asked Dan with considerable sharpness.

Penn resumed his walk and drew his light eyebrows together. “I am willing to explain as soon as you tell me why you speak of the scent.”

“Hang it, man!” rejoined Halliday, dropping into step, “any one would notice the scent and speak of it since it is so strong.”

“Oh”— Penn’s brow cleared —“I understand now. You have taken a fancy to the scent and wish me to get you some.”

Halliday was about to make an indignant denial, when he suddenly changed his mind, seeing a chance of learning something. “Well, can you get me some?”

“No,” said Penn coolly; “I cannot. This is a particular perfume which comes from the Island of Sumatra. I have a cousin there who knows that I like perfumes, and he sent me a single bottle.”

“Can’t I buy it anywhere?”

“No, it is not to be obtained in England,” said Penn curtly.

“In that case,” said Halliday slowly, “it is strange that I should have smelt the same perfume on the clothes of Sir Charles after his death.”

“Did you?” Penn looked surprised. “That is impossible. Why, Sir Charles detested scents, and I never dared to use this one until I left him for the night.”

“You used it on the night of the murder?”

“Of course. I used it every night when I left Sir Charles. On that evening he sent me away with my usual batch of letters, and was going down to the House later. I would not have seen him until the next morning, so I took the opportunity to indulge in this taste.”

“Then how did Sir Charles’s clothes become impregnated with it?”

“I am unable to say. Why do you ask? Surely”— Penn turned an alarmed face towards the speaker, and looked yellower than ever —“surely you do not suspect me of keeping back anything from the police likely to lead to the detection of the assassin.”

“Ask yourself, Mr. Penn,” said Dan coldly. “I and Inspector Tenson and Mr. Durwin smelt this particular perfume on the clothes of the dead man, and I do not mind telling you that the police consider it to be something of a clue.”

“A clue to what? To me? It must be, since I alone possess this scent. I certainly came into the library when summoned by Mr. Durwin, and I helped to look after Sir Charles. As I was strongly perfumed with the scent it is not impossible that my employer’s clothes took what, doubtless, you will call the taint. I think,” ended Penn in a dignified manner, “that such is the proper explanation. You have found a mare’s nest, Mr. Halliday.”

“Upon my word, I believe I have,” said Dan, quite good-humouredly, “but you must forgive me, Mr. Penn. Inspector Tenson agreed with me that the fly and the scent were clues.”

“About the fly I know nothing,” said the secretary positively, “but this scent is not to be had in England, and Sir Charles’s clothes could only have gathered the fragrance from mine. If Inspector Tenson suspects me —”

“No, no, no!” interrrupted Halliday quickly. “I assure you that he does not.”

“He would if you told him of our meeting,” retorted Penn as they passed into Piccadilly Circus, “and as I don’t like even a suspicion to rest on me, Mr. Halliday — for my good name is my fortune — I shall go and see him and explain the whole circumstance. Indeed, if he wishes it, I shall give him the bottle which my cousin posted to me from Sumatra, and never shall I use the scent again. I do not like these injurious suspicions.”

“Don’t make a mountain out of a mole-hill,” said Dan, drily; “if I have hurt your feelings, I apologise.”

“I accept your apology only on condition that you accept my explanation.”

Dan inwardly chuckled at Penn’s dignity, but replied readily enough. “Oh, yes, for if I did not accept your explanation I should not make any apology. You are probably right since the scent must have got on to Sir Charles’s clothes from your own. The clue — as we took it to be-has ended in smoke.”

“But don’t you think that I should see Inspector Tenson and explain?”

“There is no need,” Dan assured him, soothingly. “If the Inspector says anything about the scent, I shall explain; and, after all, it was I who suggested the perfume as a clue.”

“Would you like what is left of the bottle?” asked Penn, pacified by the very frank apology of the other.

“No, thanks, I never use perfumes. I hate them.”

“So did Sir Charles,” mused Penn, and eyeing Dan with a lack-lustre gaze. “I wonder he did not suspect me of liking them. If he had come upon me scented in this manner, he would have kicked me out.”

“It is to be hoped Lord Curberry has not the same dislike,” said Dan, who having learned all he wished, desired to escape from such boring society.

“No, he has not,” said Penn with great simplicity; “he is very kind to me. I suppose he will marry Miss Moon.”

“Then you suppose wrong. He will not,” snapped Halliday roughly.

“He loves her devotedly,” insisted the secretary, and with a glint of malice in his pale-coloured eyes.

“Good day,” rejoined Dan shortly, as he did not wish to argue the matter. He turned into Regent Street — for by this time they had crossed the Circus — when Penn ran after him and seized his arm.

“Is there any chance of the woman who killed Sir Charles being found?”

“No,” replied Dan, halting for a moment. “Why?”

“Because Sir Charles was good to me, and I should like his death to be avenged. That is only natural. Surely the police will search.”

“They are searching, Mr. Penn, and can discover nothing.”

“Perhaps Lord Curberry may hunt for this woman. I shall ask him to, and as he loves Miss Moon so devotedly, he will try and learn the truth.”

Irritated by this speech — for Penn knew all about the rivalry — Dan became scarlet. “I shall discover the truth. Lord Curberry need not trouble himself.”

“If you discover the truth —” began Penn, and hesitated.

“Well?” asked Halliday sharply.

“I think Lord Curberry will certainly marry Miss Moon.”

“What do you mean by that?” demanded Dan, but Penn gave no answer. Shaking his head significantly, he stepped back, and in one moment was lost in the midst of the crowd which thronged the corner. Halliday would have followed, for the man’s last observation seemed to hint that he knew more about the truth than he was disposed to admit; but many people came between him and the secretary, so it was impossible to get hold of him again. Dan was forced to walk on alone and he walked on pondering deeply.

Did Penn know the truth? It seemed impossible that he should know it. The evidence of the typewriting girl went to show that he had not left his private room all the evening until summoned by Durwin when the death was discovered. What Penn said about the perfume appeared to be reasonable enough, as he certainly had handled the body, and if reeking of the scent — as he was reeking on this very day — it was not surprising that the odour should communicate itself to the dress clothes of the dead man. Some odours cling very powerfully, and endure for a considerable time. This Sumatra scent assuredly had done so, for it was quite three hours after the death that Dan himself had seen the corpse, and even then he had smelt the perfume. However, on the face of it, Halliday saw no reason to doubt Penn’s statement, and quite understood how he became, through Sir John’s mediation, the secretary of Lord Curberry. Only the last speech of the secretary was strange. Why should he say that, if the truth were discovered by Dan, Curberry would marry the girl, when, on the discovery of the truth — so far as Dan could see — the marriage of himself to Lillian depended? Dan could find no answer to this question, and had half a mind to follow Penn to his new employer’s house, so as to force an explanation. But as he knew Curberry did not like him, he decided to let matters stand as they were, and only reveal what he had heard to Laurance.

For the next four or five days, young Halliday went about his business in a quiet, determined manner, and thought as little as possible of Lillian. He did not even write or call to see her, since he wished to give up his whole attention to discovering the truth about Moon’s death. If he thought of love and Lillian, he certainly could not concentrate his mind on the necessary search. And such attention was very necessary, if he intended to marry the girl. He became certain that in some way Sir John intended to trick him, but if he found out the false Mrs. Brown, and solved the mystery, Sir John would be forced out of sheer justice to sanction the marriage. It was heroical of Halliday to turn his thoughts from his beloved and it was no easy task to one so deeply in love as he was. But he saw the need of it, and manfully set himself to endure present pain for future joy. Whether Lillian saw things in the same light, or resented his neglect, he did not know, as he had no word from her; neither came there any letter from Mrs. Bolstreath. Dan had certainly been pushed out of the girl’s life by her astute uncle; but it was his own common sense that kept him out of it; for the time being — be it understood. Love demands its martyrs and Halliday had become one for Love’s sake. By doing so, although he knew it not, he was displaying more real love towards her than he had ever done in his life before.

Meanwhile, Laurance lost no time in publishing his letter, which dealt with the mystery of Moon’s death. As “The Moment”, including its extra letter-writing sheet, had a large circulation, and as it was a season devoid of news, the letter caused great discussions. It was sufficiently alarming to those who loved law and order, since it boldly announced that a gang of criminals existed which coldly and cautiously and deliberately employed its members to put people to death. The letter called attention to the fly — and that an artificial one — on Sir Charles’s neck near the poisoned wound, and declared that such was the sign-manual of the accursed society. No mention was made of the scent, since Dan had explained what Penn had said to Laurance, and Laurance had accepted the explanation as valid. But there was quite enough in the letter to startle the most dull, especially when the writer called attention to the happening of various mysterious murders, and suggested that such were the work of this misguided set of people who constituted the unknown gang. Finally, Freddy ended his letter by saying that Moon had knowledge of the gang, and had sent for a Scotland Yard official — name not given — to explain the whole matter, when he met with his death. It was a fact, therefore, that the false Mrs. Brown was an emissary of the gang who had been detailed to murder Sir Charles and had performed her vile errand only too well. A postscript to the epistle invited discussion, and particularly called upon any person who knew of an artificial fly being found on a corpse to give evidence.

In two days the sheet was filled with letters from various people, and the matter was much discussed. Some of the writers laughed at the idea of such a society existing in a civilised country such as England was, while others expressed alarm and asked what the police were doing not to arrest the criminals. These last scribes evidently entirely forgot that no one knew where the central quarters of the gang were, and that the letter of Mr. Laurance was an attempt to root out the heart of the mystery. Those who appeared in print and aided the circulation of “The Moment” by buying their own lucubrations certainly did not help much. The generality of the letters were discursive and ornate, wandering very much from the point, and giving no positive information such as would assist Freddy’s purpose. But three or four epistles drew attention to certain mysterious crimes, the perpetrators of which had never been brought to justice, and who were not even known. There was the case of a young girl found dead on the Brighton railway line near Redhill, and who must have been thrown out of the train. Then someone wrote about a miser in the East End who had been strangled, and another person recalled the drowning of a well-known philanthropist in the Serpentine. A verdict of suicide had been brought in as regards this last victim, but the writer of the letter positively asserted that the philanthropist had not the slightest intention of making away with himself. Finally came a batch of letters concerning children who had been murdered.

But only in one case did it appear that any fly was seen on the victim, and that was when a schoolmistress was stabbed to the heart while in bed and asleep. The assassin had entered and escaped by the window, and the victim’s mother — who wrote the letter drawing attention to this case — had found the fly on her daughter’s cheek. She had thought nothing of it at the time, and had brushed away the insect. But after the mention of the fly on Sir Charles Moon’s neck, she remembered the incident. Also it turned out that the schoolmistress, had she lived, would have inherited a large sum of money. It was this last circumstance that suggested the intervention of the gang to murder the girl so that someone else might inherit. But all the letters dealing with the various cases were vague, and no enlightening details could be given. All that could be said was that there were many unusual deaths, the mystery of which could not be solved. Laurance, reading the letters during the week of their appearance, felt sure that the gang existed, but he was more or less alone in his opinion. Even Dan was doubtful.

“It seems such a large order for a number of people to band themselves together in order to murder on this comprehensive scale,” he objected; “and I don’t quite see the object. Many of the victims mentioned in these letters are poor.”

“You seem to have changed your mind about the matter,” said Laurance drily, “for when my letter appeared you were assured that there was such a gang.”

“Only because of Sir Charles’s remarks to Durwin.”

“It was a pity Sir Charles was not more explicit,” retorted Freddy crossly.

“He had no time to be explicit,” said Dan, patiently, “since he died before he could explain. But let us admit, for the sake of argument, that such a gang exists. Why should the members murder poor people?”

“Folks have been murdered by way of revenge, as well as for money. And let me remind you, Dan, that four or five of these victims mentioned in the letters had money, or were about to inherit money. I am quite convinced,” said Laurance, striking the table, “that there is such an association.”

“An association for what?”

“You are very dull. To get undesirable people out of the way. Remember, in the reign of Louis XIV, there were dozens of poisoners in Paris who undertook to kill people when engaged to do so. The reason was for revenge, or desire for money, or — or — or for other reasons,” ended Laurance vaguely.

“Hum!” Dan stroked his chin, “it may be as you say. Certainly Sir Charles was got rid of, because he knew too much.”

“About this gang,” insisted Laurance, “since he was to see Durwin about the same. I am certain that such an association exists.”

“You said that before,” Halliday reminded him.

“And I say it again. At all events there is one thing certain — that we have learned from these letters of many mysterious crimes.”

“But only in one case was the fly discovered,” objected Dan again.

“That is not to be wondered at,” replied the journalist; “the wonder is that such a small insect should be noticed at all. No one would ever think of connecting a fly, whether dead or alive, with the death. The mother of the schoolmistress did not, until your experience with regard to Moon was quoted in my letter. The fly business is quite ridiculous.”

“And perhaps means nothing.”

“Oh, I think it does, seeing that in Moon’s case the fly was artificial. Probably in the case of the schoolmistress it was artificial also, only the mother who noticed it did not make an examination. Why should she? I wonder the gang don’t have a better trade-mark.”

“Perhaps the gang may think it would be spotted if it did.”

“Then why have any trade-mark at all,” answered Laurance, sensibly. “If there is to be a sign, there should be some sensible one. If the fly was stamped on the skin, as the purple fern was stamped, there would be some sense in the matter. But a fly, artificial or not, is —” Freddy spread out his hands, for words entirely failed him.

“Well,” said Dan after a pause, “I don’t know what to say, since everything is so vague. However, I shall assume that such a gang exists, and shall do my best to help you to bring about its destruction, as that means my marriage to Lillian. To help, I must have money, so the sooner we get north and engage one of Vincent’s machines with all the latest improvements, the better shall I be pleased.” He moved towards the door, as they were in Laurance’s rooms when this conversation took place, and there he halted. “I think, Freddy, you will have a chance of proving in your own person, as to the truth of your supposition regarding this gang!”

“What do you mean?” asked Laurance somewhat startled.

“Well,” murmured Dan, “the gang know you started the hunt for its destruction, as I expect the members read the papers. If that is the case you will be a source of danger, such as Sir Charles was and —”

“I’ll look after myself,” interrupted Laurance grimly.

“Well, if you don’t, and the worst comes,” said Dan agreeably, “I shall carefully examine your corpse for the celebrated fly.”

“I’ll look after myself,” said Laurance again, “and if you think I am going to give up doing business through fear of death, you are much mistaken. If I can find the gang and exterminate them, I’ll get a much larger salary, and so will be able to marry Mildred.”

“Oh, that’s her name is it! Mildred Vincent! Is she pretty?”

“You might not think so since Miss Moon is your ideal,” said Freddy, with a blush. “Mildred is dark and tall, and well-proportioned — none of your skimpy women, old man.”

“Lillian isn’t skimpy,” cried Halliday indignantly.

“I never said she was. Let us call her fairy-like.”

“That’s better. And your Mildred?”

“You’ll see her when we go north the day after tomorrow.”

“Good!” Dan nodded thankfully, “we go to Vincent the day after tomorrow?”

“Yes. Meet me at a quarter to twelve at St. Pancras Station; the train leaves at mid-day and we change for Beswick about four o’clock. I expect we’ll arrive — all going well — at Sheepeak about six.”

“Good! But why shouldn’t all go well?” inquired Dan, after a pause.

Laurance chuckled. “According to you, the gang will hunt me down, and as you are in my company — well!” he chuckled again.

“Oh, I don’t care a cent for the gang, no more than yourself,” retorted Dan with a shrug. “I’m not even going to think of the beasts. We go north to get the machine which will enable me to win this two thousand. And then —”

“And then?” echoed Laurance with a grin.

“Then I shall discover the truth, crush the gang, and marry Lillian.”

In this way, therefore, the muddy water was stirred up.