A case of identity

The story revolves around the case of Miss Mary Sutherland, a woman with a substantial income from the interest on a fund set up for her. She is engaged to a quiet Londoner who has recently disappeared. Sherlock Holmes's detective powers are barely challenged as this turns out to be quite an elementary case for him, much as it puzzles Watson.
The fiancé, Mr. Hosmer Angel, is a peculiar character, rather quiet, and rather secretive about his life. Miss Sutherland only knows that he works in an office in Leadenhall Street, but nothing more specific than that. All his letters to her are typewritten, even the signature, and he insists that she write back to him through the local Post Office.
The climax of the sad liaison comes when Mr. Angel abandons Miss Sutherland at the altar on their wedding day.