Rinehart was a popular American author considered the inventor of the Had-I-But-Known school of mystery writing. Her immensely successful first novel, The Circular Staircase launched her career, and her books, which often blend mystery with humor and romance, have sold over 10 million copies. She was a war correspondent during WWI and wrote several books promoting women’s contributions to the war effort. What popular phrase is said to have been inspired by her 1930 novel The Door? Discuss
Source: The Free Dictionary