Keeper of the Keys (1932) is the sixth and last mystery in the Charlie Chan series of Earl Derr Biggers; Biggers was planning on continuing the series, but died in 1933 before he could. The films continued the series for him. Once again, the setting of the novel is rural California, where Chan has been invited as a houseguest. He meets a world-famous soprano, Ellen Ladona, who is murdered not too long after the meeting. Chan does not have far to look for suspects—the host is her ex-husband, as are three of the other house guests. Her servants, entourage and husbands all come under suspicion. Once again, Chan is expected to solve the murder, which he does by understanding the key clues…. This was the only one of Biggers' Chan novels never to be adapted into a film, while some of the others were used more than once to create films. However, it was adapted into a short-lived Broadway play in 1933, with William Harrigan playing Charlie Chan. Earl Derr Biggers (1884 – 1933) was an American novelist and playwright. He is remembered primarily for his novels, especially those featuring the Chinese American detective Charlie Chan, from which popular films were made in the United States and China. The popularity of Charlie Chan extended even to China, where audiences in Shanghai appreciated the Hollywood films. Chinese companies made films starring this fictional character. The Charlie Chan series: The House Without a Key (1925) The Chinese Parrot (1926) Behind That Curtain (1928) The Black Camel (1929) Charlie Chan Carries On (1930) Keeper of the Keys (1932)