K. is one of the first books in which Rinehart attempted to write mainstream fiction. She does not rely on the comfortable formula of the detective novel, and the tone is completely serious. She also departs from her early tendency toward romanticism in favor of realistic depiction of everyday life, especially in the hospital scenes. Her handling of plot is not sure, however, and the conclusion seems banal, sentimental, and predictable.
A film version of K. appeared in 1918 under the title The Doctor and the Woman. Six years later Universal brought out K. — the Unknown.