"Yes, he did, sir. I knocked and kicked for a long time, then I ran back to the house and found the fire had been put out."
"Did Professor McMurray ever refer to the matter?"
"He was very angry when I next saw him, sir, three days later."
"What did he say?"
"That neither fire nor murder was an excuse for interrupting him, and if I did it again I would have to——"
"Quite so," interrupted Malcolm Sage, desirous of saving the old servitor the humiliation of explaining that he had been threatened with dismissal.
"So you are confident in your own mind that no amount of knocking at the door would have caused your master to open it?"
"Quite certain, sir," the butler said with deep conviction. "If he had heard me murdering Mrs. Graham he wouldn't have come out," he added gravely. "He used to say that man is for the moment; but research is for all time. He was a very wonderful man, sir," he added earnestly.
"So that to get into the laboratory someone must have had a duplicate key?"
"No, sir, the professor always bolted the door on the inside."