"I'm not criticizing 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 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-humoredly, "but you must forgive me, Mr. Penn. Inspector Tenson agreed with me that the fly and the scent were clues."