A young woman named Mary Sutherland is engaged and about to marry Hosmer Angel, when he unexpectedly disappears. In her despair and anxiety, Mary decides to ask Sherlock Holmes for his help. This seems to be a simple case for the great detective. After a short exchange of letters with Mary's stepfather, Mr. Windibank, Sherlock finds out what the truth is. Why and how did Hosmer Angel disappear? How did the letters help Sherlock and what did he discover? Is the missing man still alive? You can find the answers in Sir Arthur Conan Doyle's short story "A Case of Identity".