While we awaited the man's return McKelvie came out of the safe and resumed his indolent pose. Again I found myself growing exasperated with his attitude. Surely there were clues to be found in the room, and he wasn't thinking because those brilliant black eyes were wide-open and wore an expression of contented ease.
"Since you object to my inactivity," he remarked quietly, "let's talk. At least we shall be exercising our tongues, if nothing more," and he laughed oddly.
I ceased trying to understand him and welcomed the opening that he gave me. "Will you answer me three questions?" I inquired.
"Depends on what they are," he returned laconically.
"Nothing really startling," I answered, laughing. "I merely wished to know why if Lee Darwin was outside that study window he did not leave footprints for the police to discover, as they did the ones that he made in the morning."
"Because there is a flower-bed under all the windows except the first two. Beneath those two the cement walk reaches to the wall. He stood on this walk that night, but in the morning having just come in the door he rushed out of the window nearest to him and stepped into the flower-bed."
"I see. Now here's question two. How did you know so unerringly that the lamp was also lighted from the safe?"
"Childishly simple. I had already deduced a secret entrance."
"How?" I broke in.
"Sherlock Holmes says, 'Exclude the impossible, whatever remains improbable must be the truth.' Mrs. Darwin didn't kill her husband or I should not be here. The case is one of murder, not suicide, therefore someone else must have been in the room at midnight. He couldn't leave by the windows or the door and flesh and blood doesn't vanish into air, ergo he must have gone out by some other entrance, natural inference a secret one, since it wasn't discovered."