She was a prolific author, but her fame rests on a single novel. The only daughter of a French barrister and an English feminist, Marie Belloc Lowndes (1868-1947) was the sister of Hilaire Belloc, the granddaughter of the painter Jean-Hilaire Belloc, and the great-granddaughter of a famous theologian who invented soda water. She was one of the first to join the Women Writers' Suffrage League, and married a Times journalist. After her husband was left a legacy of £2,000 she had the financial security to risk a writing career, and began pouring out novels, essays, plays and memoirs at a rate of one a year, (I tally her total output at around 72 volumes but there may have been more).
Lowndes proved to be brilliant at combining suspenseful, exciting plotting with psychological insight. Her novel Letty Lynton became a film vehicle for Joan Crawford, but there was another far more sensational book. In 1913, her novel The Lodger was slow to attract readers but gradually became a smash hit, eventually selling more than a million copies. It was loosely based around the Jack the Ripper murders, an outrage that had occurred just 25 years earlier and was still being discussed and analysed across the country. The book's inspiration came from a dinner party during which she overheard the hostess talking about her butler and cook, who kept lodgers and were convinced that one of them was the Ripper. In the novel, the landlady's suspicions grow when she discovers her lodger is a religious fanatic who walks the streets late at night and has an aversion to the engravings of beautiful women in his room. He reads sections of the Bible that rail against women, and returns home with a bloodstained cape. The novel's US version was championed by Gertrude Stein and Ernest Hemingway.
Sources I've read about Belloc Lowndes, including the Wikipedia article, cite two movies based on her novels: The Lodger and Letty Lynton, and neglect to mention The Story of Ivy, which was made into a movie starring Joan Fontaine with the simple title, Ivy. It was on Turner Classic Movies last week. Ivy is a scheming woman who seems quite innocent: she is married (Richard Ney), has a lover (Patric Knowles), and wants another richer man (Herbert Marshall) to replace them both. So, she had to get rid of the husband and current lover and plans what she thinks is the perfect crime. It is an elegant and stylish film, produced by William Cameron Menzies. I won't give away the plot, but you know that crime does not pay--and there are few perfect crimes. According to TCM's article on the movie, this role was originally intended for Joan Fontaine's sister and rival, Olivia de Havilland. Olivia did not want the role because Ivy, as the title card noted is "So Sweet . . . So Beautiful . . . So Lovely . . . but so utterly EVIL" and she did not want to play such an unsympathetic role.