Mary Roberts Rinehart, American author and playwright (d. 1958)
Mary Roberts Rinehart (August 12, 1876 – September 22, 1958) was an American writer, often called the American Agatha Christie. Rinehart published her first mystery novel The Circular Staircase in 1908, which introduced the "had I but known" narrative style. Rinehart is also considered the source of "the butler did it" plot device in her novel The Door (1930), although the exact phrase does not appear in her work.