Coming back to 221B Baker Street after a long walk near Hyde Park (which allowed him to get some fresh air after spending an entire week locked in his room, experimenting a new anaesthetic. He had to admit that he missed Watson's presence, who moved in with his fiancée two months ago), Sherlock Holmes immediately noticed the smell of a certain Parisian perfume which was filling the air, found broken walnuts on the dusty table, and saw that an embroidered handkerchief was covering his violin. He sighted.
This mustn't register on an emotional level, but she was back in town.