When a Man Marries

Mary Roberts Rinehart (August 12, 1876-September 22, 1958) was an American writer, often called the American Agatha Christie. She is considered the source of the phrase "The butler did it", although she did not actually use the phrase. She is considered to have invented the "Had-I-But-Known" school of mystery writing.
When a Man Marries is a romantic comedy with mystery overtones the plot unfolds as several Bright Young characters suddenly find themselves sequestered in a large house under quarantine because the butler has just been stricken with smallpox.