In "A Case of Identity," Sherlock Holmes is consulted by a young woman named Mary Sutherland. She seeks Holmes' help in finding her missing fiancé, Mr. Hosmer Angel, who mysteriously disappeared shortly before their wedding.Holmes and Watson investigate the situation and discover that Mr. Angel is not who he claims to be. They uncover that "Hosmer Angel" is a ruse created by Mary's stepfather, Mr. Windibank, who wanted to keep Mary financially dependent on him. Windibank had posed as Angel through letters to Mary, manipulating her affections.Eventually, it is revealed that Windibank had orchestrated the disappearance to prevent Mary from marrying and leaving him, thereby ensuring her income would continue to support him. Holmes exposes Windibank's deceit to Mary, advising her on how to move forward.The case concludes with Mary gaining clarity about Windibank's deception, allowing her to break free from his control and move on with her life. Holmes, once again, solves the mystery and brings justice to his client.