When I watched an episode of Wallander, ‘The Castle Ruins’, the other day, I mused again on the tricky question of how many suspects a whodunit requires. It’s a question that occupies my mind quite a bit when writing a mystery, but it is also something that matters to me as a reader or viewer.
In this episode, the Swedish cop was investigating the murder of a scruffy chap who had just withdrawn a huge sum of money from his bank account. The victim had made his loot from selling land to be turned into a luxurious beach development. But not all the residents appreciated the unlovely bloke, especially since he hung around, along with his dogs, instead of doing the decent thing and leaving them to their upwardly mobile existences.
Further murders quickly occurred, and unfortunately they served only to confirm my initial suspicion about the culprit’s identity. But this was due to no great brilliance on my part – very few other viable suspects were left.
This is the challenge, then, for the writer. To include enough potential killers in the story to retain an element of surprise, but not so many that it becomes impossible to give them clearly differentiated characters. Agatha Christie had lots of suspects in many of her books, but Cards on the Table shows that she could still ring the changes cleverly even when she confined herself to a handful. This is a topic that fascinates me, and I’m sure that it provokes a range of opinions. What is the secret – if any – to getting the right number of suspects in a mystery?