Let me paint you a picture.

You're reading a novel. The plot is ticking along nicely, the detective is being detectivey, and then you turn a page and walk into the house. And something happens. The hairs on the back of your neck do a little shimmy. The house isn't just where the story is happening — it is the story. It watches. It remembers. It has opinions about you, and they're not entirely flattering.

There is a peculiar tightrope that every cosy mystery writer must walk, and it goes something like this: on one side, a body. On the other, a joke about scones.

Every genre has its icons. Romance has its brooding dukes. Thrillers have their maverick agents with a drinking problem and a past. But cosy mysteries? We have something far more interesting: a retired spinster who knits and sees everything, a fussy Belgian with a moustache that could tell its own story, and an assortment of amateur sleuths who absolutely should not be solving murders but somehow always do.

There's a particular kind of reader who will finish a novel, set it down with a satisfied sigh, and immediately start wondering what happened to the postman.
Not the protagonist. Not the villain. The postman — the one who appeared in three scenes, delivered a pivotal letter, made a dry joke about the weather, and was never seen again. That reader will lie awake constructing an entire biography for him. A difficult childhood, perhaps. An allotment. A secret fondness for jazz.

There is a delicious irony at the heart of writing mystery fiction: the author must know exactly whodunnit, why, when, and with what blunt instrument — yet somehow contrive to feel the thrill of not knowing while the story unfolds. Get the balance wrong and the prose goes flat, like a detective who has already glanced at the back of the box before starting the puzzle. Get it right, and you find yourself genuinely surprised by your own characters, typing at speed because you simply cannot wait to see what they do next.