Earlier detective writers merely wished to astonish readers with revealed solutions and to impress them with genius, as with Holmes or The Thinking Machine. Golden Age writers, however, taking the 'puzzle' seriously, tried hard to pay fair with clues yet outsmart the reader. This duel of clever and classy detective versus clever and classy criminal in the British detective story paralleled the duel of clever writer versus careful reader. American writers, on the other hand, generally avoided the 'duel' altogether, preferring the 'brawl' and the shoot-out. Even readers feel mugged by the confused action and fast talk.
Some of the 'fair play' became quite complex. Christie, especially, played with the 'rules' as a way to outsmart readers. It was a matter of "You think that I think that you think I think this, so I won't -- or will -- in order to outwit you." (SPOILERS FOLLOW) She did things like exonerate a suspect in a trial only to prove he was guilty all along, employed double disguises, broke the convention of 'least likely suspect' in "Murder on the Orient Express" by having ALL the suspects committing the murder. She committed the unforgivable sin in "The Murder of Roger Akroyd" of making the first-person narrator the killer.
If English Golden Age writers were trying to widen the appeal of detective stories, American(s) Ellery Queen narrowed it. Instead of bending rules, Queen followed them, focused them, banishing every element but the detective and the crime puzzle. Despite a few innovations like a father cop/detective son and a secretary with a crush on her boss, Queen openly emphasized the fair play puzzle by issuing a 'challenge to the reader' near the end of each story, saying the reader now had the same clues as the detective. Queen, who began his (well, their) career by entering a contest, saw all detective stories as a contest between the reader and writer.
Queen's stories, like many Golden Age stories, fortified the puzzle element with things like maps, diagrams, lists of alibis, challenges to readers, narrative gaps that warned readers that something was missing, sealed last chapters, footnotes, lists of questions, lists of characters, and narrative warnings to pay attention (something Dickens did in Drood). The form developed into other puzzle products like "McKay's Baffle Book" and "Three Minute Mysteries", games with bits of evidence in cellophane wrappers such as hair, matches, fabrics. Parker Brothers' board game "Clue" appeared at this time and is still with us.
The Golden Age ended in 1939 with World War II. While some writers had simply stopped writing detective stories (Sayers, for example), the war changed everything. Real-life Master Criminals had loosed mass destruction on humanity. Murder had become industrialized in the Death Camps. Post-War detective fiction turned cynical (just as it had after World War I), and brutal. Christie continued writing British 'cozies' in the same way Doyle continued writing about Holmes well into the 1920s, as a kind of denial.
Golden Age stories still enjoy immense popularity, but they are nostalgic entertainments, seen as offering the stylish wit and cultured cleverness longed for by middle class readers.
Next time, we'll look closer at the Golden Age in America and consider other changes in the genre following World War II.