So saying, Murdock turned a crank which projected from the wall. A grating sound was heard, as of the rasping of metal upon metal. Then he returned to his desk, where he busied himself for a few minutes under pretext of looking for some notes of his experiments. When apparently he had found what he was seeking, he went toward the door of the extension. This was of massive hard wood. Before turning the knob, the chemist stooped as though to examine the lower hinge. Sturgis was not consciously following Murdock's movements. His mind was bent upon accomplishing a certain object; and, with that end in view, he was gradually drawing nearer to the typewriter. But so accustomed was he to receiving detailed impressions of all that occurred before his eyes, that the chemist's actions, unimportant as they seemed at the time, were unconsciously recorded upon the reporter's brain. Murdock opened the door of the extension and passed out of the room. Sturgis, watching his chance, snatched up a sheet of paper from the table, inserted it in the typewriter, and rattled off something as fast as he could. Looking up when he had finished, he saw that Murdock had returned and was observing him with a sardonic grin. "More happy thoughts?" he inquired. "Yes," answered Sturgis, calmly folding the paper and slipping it into the pocket of his coat. Murdock chuckled to himself, as if enjoying a quiet joke. "Well," said he, "if you will do me the honor, we can step down into the laboratory." Sturgis nodded and went toward the door which Murdock held open. As he passed the chemist, the reporter caught his eye, and, in a flash, read there some sinister purpose, which caused him to hesitate, on his guard. At that moment there came a knock upon the hall door. "Pshaw!" exclaimed Murdock, "here comes an interruption, I suppose. Please step down stairs; I shall be with you directly." With these words, he quietly but firmly shoved the reporter into the extension, and, with a rapid motion, pushed forward the door. Sturgis almost lost his balance, but instinctively put out his foot between the door and the jamb. He felt a strong pressure from the outside; but he knew he was master of the situation and patiently bided his time. Presently the pressure ceased, and he was able to open the door. Murdock wore an air of pained surprise. "What is it?" he inquired. "I have just remembered an important engagement," said Sturgis unruffled. "I fear, after all, that I shall be unable to visit your laboratory at present. I hope, however, that the pleasure is only postponed for a short time." "I hope so," replied Murdock, calmly meeting his steady gaze. All this had happened in the space of a few seconds. Meanwhile the knocking at the door was renewed. "Come in," said Murdock, moving toward his easy chair. The door opened and a servant appeared. "Plaze, sur, Miss Agnes wud loike ter know kin yer resave her sum toime this afthernoon?"