"A Case of Identity" is a short story by Sir Arthur Conan Doyle, first published in The Strand Magazine in September 1891. It is the third story in the collection The Adventures of Sherlock Holmes.The story concerns Miss Mary Sutherland, a young woman who comes to Sherlock Holmes for help after her fiancé, Mr. Hosmer Angel, suddenly disappears. Miss Sutherland tells Holmes that Angel is a respectable young man who works in an office in Leadenhall Street. He is a frequent visitor to her house, and she has never known him to be anything but kind and considerate.Holmes is initially puzzled by the case, but he soon discovers that Angel is not who he seems. In fact, Angel is actually James Windibank, Miss Sutherland's brother-in-law. Windibank has been posing as Angel in order to elope with Miss Sutherland's wealthy aunt.Holmes exposes Windibank's deception and helps Miss Sutherland to reunite with her true love. The story ends with Holmes reflecting on the strangeness of reality, which he says is often stranger than fiction.Here are some of the key themes of the story:

• The perception of women in Victorian-era London. Miss Sutherland is initially portrayed as a naive and gullible young woman who is easily fooled by Windibank. However, Holmes eventually comes to see her as a strong and independent woman who is capable of making her own decisions.
• The idea that reality is stranger than anything that can be written about in fiction. This theme is explored through the story's twist ending, which reveals that Angel is not who he seems.
• The importance of observation and deduction. Holmes is able to solve the case by carefully observing the details of the situation and using his deductive reasoning skills.

"A Case of Identity" is a classic Sherlock Holmes story that has been adapted many times for stage, film, and television. It is a well-crafted mystery with a suspenseful plot and memorable characters. The story is a must-read for any fan of Sherlock Holmes.