“Au revoir,” said our visitor; and with a bright, kindly glance from one to the other of us, she replaced her pearl-box in her bosom and hurried away.

Standing at the window, I watched her walking briskly down the street until the gray turban and white feather were but a speck in the sombre crowd.

“What a very attractive woman!” I exclaimed, turning to my companion.

He had lit his pipe again and was leaning back with drooping eyelids. “Is she?” he said languidly; “I did not observe.”

“You really are an automaton - a calculating machine,” I cried. “There is something positively inhuman in you at times.”

He smiled gently.

“It is of the first importance,” he cried, “not to allow your judgment to be biased by personal qualities. A client is to me a mere unit, a factor in a problem. The emotional qualities are antagonistic to clear reasoning. I assure you that the most winning woman I ever knew was hanged for poisoning three little children for their insurance-money, and the most repellent man of my acquaintance is a philanthropist who has spent nearly a quarter of a million upon the London poor.”

“In this case, however- -”

“I never make exceptions. An exception disproves the rule. Have you ever had occasion to study character in handwriting? What do you make of this fellow’s scribble?”

“It is legible and regular,” I answered. “A man of business habits and some force of character.”

Holmes shook his head.

“Look at his long letters,” he said. “They hardly rise above the common herd. That d might be an a, and that l an e. Men of character always differentiate their long letters, however illegibly they may write. There is vacillation in his k’s and self-esteem in his capitals. I am going out now. I have some few references to make. Let me recommend this book - one of the most remarkable ever penned. It is Winwood Reade’s Martyrdom of Man. I shall be back in an hour.”

I sat in the window with the volume in my hand, but my thoughts were far from the daring speculations of the writer. My mind ran upon our late visitor - her smiles, the deep rich tones of her voice, the strange mystery which overhung her life. If she were seventeen at the time of her father’s disappearance she must be seven-and-twenty now - a sweet age, when youth has lost its self-consciousness and become a little sobered by experience. So I sat and mused until such dangerous thoughts came into my head that I hurried away to my desk and plunged furiously into the latest treatise upon pathology. What was I, an army surgeon with a weak leg and a weaker banking account, that I should dare to think of such things? She was a unit, a factor - nothing more. If my future were black, it was better surely to face it like a man than to attempt to brighten it by mere will-o’-the-wisps of the imagination.