As he hurried down Michigan Avenue now, he was considering how affairs had changed with him in the last six months. Then he had been a callow assistant in a psychological laboratory. The very professor whom he had served had smiled amusedly, almost derisively, when he had declared his belief in his own powers to apply the necromancy of the new psychology to the detection of crime. But the delicate instruments of the laboratory—the chronoscopes, kymographs, plethysmographs, which made visible and recorded unerringly, unfalteringly, the most secret emotions of the heart and the hidden workings of the brain; the experimental investigations of Freud and Jung, of the German and French scientists, of Munsterberg and others in America—had fired him with the belief in them and in himself. In the face of misunderstanding and derision, he had tried to trace the criminal, not by the world-old method of the marks he had left on things, but by the evidences which the crime had left on the mind of the criminal himself. And so well had he succeeded that now he could not leave his club even on a Sunday, without disappointing somewhere, in the great-pulsating city, an appeal to him for help in trouble. But as he turned at the corner into the entrance of the club, he put aside this thought and faced the doorman.
"Has she called again?"
"The last time, sir, was at nine o'clock. She wanted to know if you had received the note, and said you were to have it as soon as you came in."
The man handed it out—a plain, coarse envelope, with the red two-cent and the blue special delivery
