6 key conventions common to murder-mystery plots

Murder mysteries hold us in thrall. Suspense keeps us hooked, while working out whodunnit is a brainteaser. On a deeper level, there is tension between our dark fascination with death and our wish to believe morality will triumph. Authors manipulate the conventions of the genre to play on these responses and keep us turning the page.

Most murder stories start with news of a death. A gruesome murder instantly gets attention and sets off questions: Who was she? Why her? Why now? Often the victim turns out to have many sides to his or her history or character, which are embedded as clues in the plot.

Traditional murder mysteries have two main sub-genres. The classic English model takes place in genteel society and in a closed place – a sealed room, a country house or a transcontinental train. It’s a theatrically contrived stage set where the characters move as in a stately dance and the plot is solved by brainpower. The realist model, often American, usually takes place in a seedy urban underworld, a tough scene for violent action and gritty heroism. Contemporary mysteries often choose more ordinary settings, such as market towns, schools or hospitals, to make the reader shudder with the realisation that all is not as unfamiliar as it seems.

The detective or private investigator is always a singular character. He or she may be an intellectual loner like Sherlock Holmes, or a hard-bitten cynical American, or a feisty woman who is tougher than she looks. There may be a sidekick like Holmes' Dr Watson, a more approachable companion whose role is to set off the brilliance of the main character and drop clues for the reader.

There are usually several suspects, each with their own motives. Exploring their characters and alibis adds depth to the novel or play. It further entangles us in the plot by making it difficult to know whether to think of the suspects with sympathy or condemnation.

Typically, an unknown murderer commits a crime. It baffles the ordinary police, until the hero comes to the rescue. Along the way, clues and false clues lead the sleuth and the reader in many different directions. The “red herrings”, are essential to keeping us intellectually and emotionally hooked, as they make us keen to follow the clues through and frustrate us when they lead nowhere.

The end of a murder-mystery plot must be a surprise -- the murderer must be the person we least suspect, or the victim must have had a secret that explains everything. The revelation should be morally and intellectually satisfying -- the murderer is found and punished, missed clues are revealed and order is restored.