Mary Sutherland, who possesses a substantial income from the interest on a fund set up for her, comes to Sherlock Holmes and Dr. Watson for help after her fiancé, Hosmer Angel, disappeared on their wedding day. Taking the case, Holmes discovers Sutherland knew little of Angel; only that he is a quiet and secretive Londoner who works at a Leadenhall Street office, communicated to her through typewritten letters, insisted that she write back via the local post office, and only met with her whenever her young disapproving stepfather and trustee of her inheritance, James Windibank, claimed he was out of the country on business.
Holmes easily deduces that Windibank and Angel are the same individual. After Sutherland's father died and he became a trustee, Windibank used her inheritance to finance his lifestyle. Upon realizing he can only do so until she leaves her home, he masqueraded as Angel before faking his disappearance. Despite solving the mystery, Holmes chooses not to divulge his findings to Sutherland, knowing she will not believe him anyway. He advises her to forget about Angel, but she refuses and holds out hope that he will return. Holmes predicts that Windibank will continue his criminal affairs until he is eventually captured and hanged.
Story from Arthur Conan Doyle - The Adventures of Sherlock Holmes in 1891.