“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?”