"The night-clerk at the Waldorf had furnished us with our first clew. On the night of my aunt's death he had seen a tall, grave-faced man hurriedly leave the hotel. As the man passed the desk he removed his hat and mopped his forehead, and the night-clerk noticed that in the middle of his head there was a patch of hair as white as snow.
"We worked this clew for all it was worth, and, a month later, I received a cable despatch from Paris, saying that a man answering to the description of the Waldorf suspect had offered an enormous crimson diamond for sale to a jeweller in the Palais Royal. Unfortunately the fellow took fright and disappeared before the jeweller could send for the police, and since that time McFarlane in London, Harrison in Paris, Dennet in Berlin, and Clancy in Vienna had been chasing men with white patches on their hair until no gray-headed patriarch in Europe was free from suspicion. I myself had sleuthed it through England, France, Holland, and Belgium, and now I found myself in Antwerp at the Hôtel St. Antoine, without a clew that promised anything except another outrage on some respectable white-haired citizen. The case seemed hopeless enough, unless the thief tried again to sell the gem. Here was our only hope, for, unless he cut the stone into smaller ones, he had no more chance of selling it than he would have had if he had stolen the Venus of Milo and peddled her about the Rue de Seine. Even were he to cut up the stone, no respectable gem collector or jeweller would buy a crimson diamond without first notifying me; for although a few red stones are known to collectors, the color of the Crimson Diamond was absolutely unique, and there was little probability of an honest mistake.
"Thinking of all these things, I sat sipping my Rhine wine in the shadow of the yellow awnings. A large white cat came sauntering by and stopped in front of me to perform her toilet, until I wished she would go away. After a while she sat up, licked her whiskers, yawned once or twice, and was about to stroll on, when, catching sight of me, she stopped short and looked me squarely in the face. I returned the attention with a scowl, because I wished to discourage any advances towards social intercourse which she might contemplate; but after a while her steady gaze disconcerted me, and I turned to my Rhine wine. A few minutes later I looked up again. The cat was still eying me.
"'Now what the devil is the matter with the animal,' I muttered; 'does she recognize in me a relative?'
"'Perhaps,' observed a man at the next table.
"'What do you mean by that?' I demanded.
"'What I say,' replied the man at the next table.
"I looked him full in the face. He was old and bald and appeared weak-minded. His age protected his impudence. I turned my back on him. Then my eyes fell on the cat again. She was still gazing earnestly at me.
"Disgusted that she should take such pointed public notice of me, I wondered whether other people saw it; I wondered whether there was anything peculiar in my own personal appearance. How hard the creature stared! It was most embarrassing.
"'What has got into that cat?' I thought. 'It's sheer impudence. It's an intrusion, and I won't stand it!' The cat did not move. I tried to stare her out of countenance. It was useless. There was aggressive inquiry in her yellow eyes. A sensation of uneasiness began to steal over me—a sensation of embarrassment not unmixed with awe. All cats looked alike to me, and yet there was something about this one that bothered me—something that I could not explain to myself, but which began to occupy me.