I found some amusing similarities between the primary romances featured in the Sherlock Holmes' adventures and the adventures of Richard Hannay. The former was written prior to the latter.
1. Both Richard Hannay and John Watson fall in love with girls named "Mary."
2. Both men are struck by her beauty and remark upon the fact that their male friend doesn't notice it.
Here Watson recounts his conversation with Holmes just after Mary left in The Sign of Four:
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 win- ning 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."
Here Richard Hannay recounts his first encounter with Mary in Mr. Standfast:
Someone put a tea-tray on the table beside us, and I looked up to see the very prettiest girl I ever set eyes on....She smiled demurely as she arranged the tea-things, and I thought I had never seen eyes at once so merry and so grave. I stared after her as she walked across the lawn, and I remember noticing that she moved with the free grace of an athletic boy.
'Who on earth's that?' I asked Blaikie.
'That? Oh, one of the sisters,' he said listlessly. 'There are squads of them. I can't tell one from another.'
Nothing gave me such an impression of my friend's sickness as the fact that he should have no interest in something so fresh and jolly as that girl.
3. These excepts lead to the third point: both men watch their Mary walk away.
4. Both men get lost in reveries about her.
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. (The Sign of Four)
In Charing Cross Road I thought of Mary, and the brigade seemed suddenly less attractive. I hoped the war wouldn't last much longer, though with Russia heading straight for the devil I didn't know how it was going to stop very soon. I was determined to see Mary before I left, and I had a good excuse, for I had taken my orders from her. The prospect entranced me, and I was mooning along in a happy dream, when I collided violently with in agitated citizen.
Then I realized that something very odd was happening.
There was a dull sound like the popping of the corks of flat soda-water bottles. There was a humming, too, from very far up in the skies. People in the street were either staring at the heavens or running wildly for shelter. A motor-bus in front of me emptied its contents in a twinkling; a taxi pulled up with a jar and the driver and fare dived into a second-hand bookshop. It took me a moment or two to realize the meaning of it all, and I had scarcely done this when I got a very practical proof. A hundred yards away a bomb fell on a street island, shivering every window-pane in a wide radius, and sending splinters of stone flying about my head. I did what I had done a hundred times before at the Front, and dropped flat on my face. (Mr. Standfast)
Yes, General Hannay, the career soldier, was so lost in thoughts about Mary that he didn't notice the air raid right away.
5. Both men marry their Mary and then she's suddenly much less of a distraction.
6. Both men are/were soldiers.