In "The Return of Sherlock Holmes," Sherlock Holmes surprises Dr. Watson with the news of his engagement, though it is not to a traditional partner but to Milverton's housemaid. This revelation takes Watson aback, as he perceives Holmes as someone who would not typically enter into marriage. The engagement seems to be tied more to Holmes's pursuit of information rather than a romantic relationship.
Holmes's unconventional announcement highlights his unique character; he is often focused on his investigations rather than personal connections. Watson's initial reaction of congratulation reflects his surprise and perhaps his understanding of Holmes's unorthodox ways. The engagement showcases Holmes's resourcefulness and determination to gather intelligence, underscoring his skills as a detective.