"Well, I wish everyone could make a statement like that," he said approvingly. "It would save us a lot of trouble in the course of the year." He leaned forward, and ran his eye over the various notes which he had jotted down while Colin was speaking. "This other burglary that the housekeeper referred to," he inquired; "when did that take place?" "I think it was about three months ago," said Colin, after a moment's reflection. "I wasn't here at the time; in fact, there was no one else in the house except Mrs. Ramsay and the cook. That was really the chief reason why the Professor decided to engage an assistant." "Why weren't the police notified?" demanded the Inspector. "There was certainly no report sent in to the Yard." "The Professor declared that he didn't want to waste his time. He was a very busy man, and as nothing appeared to have been stolen he decided to let the whole matter drop." "Nothing stolen!" repeated Marsden, raising his eyebrows. "Are you perfectly certain about that?" "It's what he told me, anyhow," replied Colin. "According to him, the only damage they did was to smash open his desk and search his papers." Both men glanced across the room in the direction of the oak bureau. "Is that the desk?" inquired the Sergeant. Colin nodded. "Had he any idea what they were after?" "Not the slightest. All his papers which are of any scientific value are kept in the laboratory. I believe he had some money and valuables in the safe, but they seem to have left that entirely alone." There was a brief silence, and then, without saying anything, the Sergeant got up from his chair and walked over toward the two pieces of furniture in question. Marsden remained seated, his keen blue eyes fixed thoughtfully upon Colin's face. "What's your opinion, doctor?" he asked at last. "I am inclined to agree with Mrs. Ramsay," said Colin. "I think it was the same man who broke into the house before. He is evidently searching for some particular paper or document, and as he couldn't find it in the desk he came back a second time to try and open the safe. On his first visit he probably hadn't got the necessary tools with him." "And how about the murder?" Colin hesitated. "There's one thing I don't understand," he frankly admitted. "I left the Professor working in the laboratory, and it's a mystery to me how he managed to reach the study without my hearing him. I was awake the whole time, and I can swear that there wasn't a sound." "Well, I can explain that to you," said the Inspector. "Mr. Carter didn't cross the hall; he entered the room by the window." With a sudden exclamation Colin started to his feet. "By Jove, what an idiot I am!" he exclaimed. "I never thought of that. Of course, there's a side door from the laboratory into the garden."