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A Scandal in Belgravia shows the deep and everlasting love that Sherlock has for one woman. A woman he loves above all others, and who he admires, respects and will do his utmost to protect from any harm (physical or emotional). That woman is ... Mrs Hudson.
Scene in 221B kitchen:
Shame on you, John Watson.
Shame on me?
Mrs Hudson leave Baker Street? England would fall.
Sherlock puts his arm around Mrs Hudson in a loving and protective embrace.
- A Scandal in Belgravia, Sherlock Series 2, Steven Moffat
To read more, follow the link to the Official BBC Sherlock website for Series 2:
And something for the purists:
To Sherlock Holmes she is always THE woman. I have seldom heard him mention her under any other name. In his eyes she eclipses and predominates the whole of her sex. It was not that he felt any emotion akin to love for Irene Adler. All emotions, and that one particularly, were abhorrent to his cold, precise but admirably balanced mind. He was, I take it, the most perfect reasoning and observing machine that the world has seen, but as a lover he would have placed himself in a false position. He never spoke of the softer passions, save with a gibe and a sneer. They were admirable things for the observer--excellent for drawing the veil from men's motives and actions. But for the trained reasoner to admit such intrusions into his own delicate and finely adjusted temperament was to introduce a distracting factor which might throw a doubt upon all his mental results. Grit in a sensitive instrument, or a crack in one of his own high-power lenses, would not be more disturbing than a strong emotion in a nature such as his. And yet there was but one woman to him, and that woman was the late Irene Adler, of dubious and questionable memory.
- A Scandal in Bohemia, The Adventures of Sherlock Holmes, Sir Arthur Conan Doyle