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.