From the first day I met her, she was the only woman to me. Every day of that voyage I loved her more, and many a time since have I kneeled down in the darkness of the night watch and kissed the deck of that ship because I knew her dear feet had trod it. She was never engaged to me. She treated me as fairly as ever a woman treated a man. I have no complaint to make. It was all love on my side, and all good comradeship and friendship on hers. When we parted she was a free woman, but I could never again be a free man.
As you have no doubt frequently observed, Watson, the impression usually goes through — a fact which has dissolved many a happy marriage.
When a man has special knowledge and special powers like my own, it rather encourages him to seek a complex explanation when a simpler one is at hand.
One should always look for a possible alternative, and provide against it. It is the first rule of criminal investigation.