Mary Roberts Rinehart

Mary Roberts Rinehart 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 earliest known source of the phrase "the butler did it", in her novel The Door, although the exact phrase does not appear in her work and the plot device had been used prior to that time.