“I do, indeed,” said Hanslet warmly. “What’s more, the Home Office people say that a dose of the stuff would produce almost immediate paralysis, and death within a few minutes. The incrustation was potassium carbonate all right, almost certainly the result of putting caustic potash on the place. But that only makes the business more puzzling. If Copperdock poisoned himself, how did he have time to apply the caustic potash before he was paralysed? If someone else did it, why should they apply the caustic, and how did they get in and out of the house? Remember, Whyland’s man Waters had the place under observation all the time.” “Then you are inclined to favour the theory of suicide?” asked the Professor. “On the whole, yes,” replied Hanslet. “Oh, by the way, I forgot to tell you that soon after daylight Waters found the syringe, with the other part of the needle still in it, by the side of the road under Copperdock’s window. There had been a heavy shower of rain about half past three, and the syringe was covered with mud and filth. The analysts could not find any traces remaining of the poison, but the end of the needle proved that it was the one that had been used. That points to suicide, a murderer wouldn’t chuck away his weapon like that where anyone could see it. “Besides, if you come to think of it, suicide fits in best with what we know. It is a fact that Copperdock’s mind was to some extent unhinged. He declared that he met the black sailor, when a reliable witness declares that no such person was about. In fact, the only person besides Copperdock who seriously claims to have seen this black sailor is a degenerate youth who is also a convicted pick-pocket. It is highly probable that the counters were numbered, and the envelopes containing them typed in Mr. Copperdock’s office. Whyland assures me that the only link between the victims was Copperdock, not in any definite form, certainly, but still definite enough to make the coincidence remarkable. I am inclined to believe that Copperdock was at the bottom of it all somehow. My difficulty will be to prove it.” “You think, I gather, that this Mr. Copperdock suffered from a peculiar form of homicidal mania, which finally culminated in his taking his own life?” suggested the Professor. “I admit that such cases are not unknown, but the theory involves you in many difficulties. I mention only one of them, the first that occurs to me. Where did he obtain this synthetic alkaloid? These substances are not articles of commerce, they are not, so far as I am aware, used in medicine. They are only produced experimentally in research laboratories. Farwell had a well-equipped laboratory, as you probably remember, which accounts for his use of such a poison. But how could a man in Copperdock’s position procure it?”