"Certainly. I thought I was mistaken at first, but he came back again, as you observed. I thought you looked uneasy while I was talking," he said laughing.
I reddened. "It wasn't very pleasant to feel his eyes on me and be forbidden to see who it was. You were facing the safe. You saw him?" I questioned.
"No, I didn't see him. He was too clever to risk that. He knew we were there, and he came to find out how much progress we had made toward putting him behind the bars where he belongs," retorted McKelvie grimly.
"You don't mean to tell me that it was the criminal himself who had the nerve to come there to-night?" I said.
"It must have been, for who else has a key to those doors? Remember that he took Darwin's key, and mine is the only other one that will open those locks. Also he would be too clever to take anyone else into his confidence," he replied.
"How did he know the combination that you used?" I continued.
McKelvie laughed. "When I locked the safe the other day I used the word, Darwin, the one you suggested. He has since made himself acquainted with that combination. Just as he was too clever to change it so that I would believe the safe untampered with, so was I too clever to let him know that I suspected his visits."
I nodded. "Why didn't you go over to the safe and capture him then?" I asked. "You missed an opportunity."
"What happened when we chased him before? The moment he saw us making for the safe he would be gone. Besides, I was playing a little game. I had put him on his guard by hunting for him. I decided to trick him into thinking that I no longer had any interest in him."
"Then all that very convincing conversation——"