Answer: Boring Plots

It would be easy to assume that the “ten commandments” of the golden age of detective fiction, a period which covered the early 20th century up into the 1930s, would have something to do with ethics, morality, or politics given the social mores of the time.

Detective fiction in the era was serious business, however, and the ten commandments, as prescribed by popular detective fiction author Ronald Knox, were all about giving the customers in the detective fiction reading business the best bang for their buck.

Among the rules were: the source of the mystery should never be a supernatural agent, no more than one secret passageway or hidden room could figure into the story, the detective must never be helped in solving the crime by a fortunate accident or happenstance, the detective must always declare the clues he discovers to the reader, and the sidekick (the proverbial Watson) must never conceal his thoughts from, nor should he be smarter than, the reader.

If that all seems a bit overly structured to you, it’s important to consider the state of the genre at the time. Detective fiction was incredibly popular, read by millions, and, in a way, almost like a game to the reader. Readers wanted a similar experience each time, they wanted to flex their mental muscles as they followed along with the familiar game-like-structure of the plot development, and they wanted to be curious companion detectives in the story right up unto a satisfying end.

Although elements of the golden age of detective fiction persist in modern story telling, the genre as a whole went into decline with the start of World War II; the start of the global conflict was the beginning of the end for the light-hearted story telling and who-done-it vehicle that drove the genre.