A first instance occurs when Miss Morstan, Holmes, Watson, and Thaddeus Sholto go to Pondicherry Lodge at night. There, on the grounds of the property, they hear what Watson calls the "saddest" and "most pitiful of sounds," which is the "whimpering" of a woman who is frightened.

At this point, Watson wants to help and protect Miss Morstan, and he takes her hand instinctively just as she is reaching for his. He states,

A wondrous subtle thing is love, for here were we two who had never seen each other before that day, between whom no word or even look of affection had ever passed, and yet now in an hour of trouble our hands instinctively sought for each other. I have marvelled at it since, but at the time it seemed the most natural thing that I should go out to her so ...

Watson also worries about asking her to marry him when she is rich and may have the Agra fortune from India coming her way. He says,

If Holmes's researches were successful, she would be an heiress. Was it fair, was it honourable, that a half-pay surgeon should take such advantage of an intimacy which chance had brought about? Might she not look upon me as a mere vulgar fortune-seeker?

Watson wants to be the one to take care of and provide for her, the traditional Victorian male role. Her wealth, as he notes, becomes a barrier between them, and he does not want asking her for her hand to be misinterpreted. Therefore, through much of the action, he feels conflicted. He knows he is duty-bound to do all he can to help Holmes locate her fortune. At the same time, he can't help but hope that Holmes will fail, unlikely as that is.

Thus, when Miss Morstan tells him her treasure is lost, Watson feels happy. At this point, he is liberated to tell her of his love and of his desire to care for her. He feels that because she lost a treasure, he has gained a treasure, which is her.