K. is a crime novel by the American writer Mary Roberts Rinehart (1876–1958) set in post-Victorian era Allegheny, Pennsylvania, which has been a part of the city of Pittsburgh since 1907. The novel tells the story of Sidney, who takes in a boarder with the initial K. and whose presence leads to mystery. A film version of K., starring Virginia Valli and Percy Marmont, was released on 17 November 1924 by Universal Pictures as a "Universal Jewel" release,