I received a note this week. "Enjoy your column on Sunday, smarty," it said, "because it will be the last column you ever write."

I pondered the note for some while, and discussed it with friends, and we came to the conclusion that it was some form of threat.

We are astute around these parts. We know a menacing tone of voice when we hear one, even if it is in a note. But what could it mean?

Is it a debt collector coming round to sever my typing finger? Is it the TV licence inspector, switching from his current tactic of pressing his lips to the keyhole and yelling: "I know you're in there! I can hear The Bold And The Beautiful! You'll have to come out some time!" Could it be my mother?

Hard to tell, really, but I rather doubt it is any of these people.

Even finger-severing debt collectors and licence inspectors generally have the self-respect to attach their names to their notes, and my mother would have used stronger language and more direct threats.

No, I think what we are dealing with here is an anonymous letter writer. Ah, they are a peculiar breed, anonymous letter writers.

They skulk, for the most part, like tubby gnomes in the undergrowth, rubbing their little hands together, patting their bellies and congratulating themselves on how diabolically clever they have been.

Generally they stay undercover, unless of course they take it into their heads that sufficient of a pack has been raised against the quarry, at which point they suddenly emerge with head thrown back in triumphant cry, brushing the gardenia leaves from their clothing, so that for all the world no one would think they had been skulking. Or so, at any rate, I gather.

That is how it was on Midsomer Murders (DSTV; Hallmark Channel; Saturdays; 8pm) a short while back. At least I think it was on Midsomer Murders, or perhaps it was A Touch Of Frost (Hallmark Channel; Fridays; 9pm). Or Inspector Morse (Hallmark; Sundays; 8pm). One of them, at any rate.

In a small village in the countryside, where no one really knows anyone else but everyone knows your business, a poison-pen campaign arises around one of the village folk.

With enough huff, puff and joyful indignation on the part of his neighbours, the inevitable happens very quickly. The campaign becomes a kind of small-hearted local cause celebre, and so excited are villagers about the hoo-hah and fol-de-rol that they forget to examine the campaign itself, and don't trouble to note that the allegations are framed - as such allegations generally are - in such a way as to pre-establish the criteria for guilt: criteria which to an outside eye in possession of the facts would hardly stand scrutiny.

And of course, equally inevitably, the villager at the centre of the storm finds himself in the traditional quandary: to respond to the allegations is to imply that the allegations are - in the way they are framed - valid.

To protest against the framing of the allegations sounds like sophistry. To keep silent is as good as throwing yourself from a bridge with rocks in your pockets and a note pinned to your chest saying, "Mea culpa". And so the tensions build.

Even when it can be demonstrated that there is no wrongdoing, it makes no difference. The affair is feeding on itself, as is the function and purpose of such affairs, and the crowd demands blood. Naturally, sooner or later they will receive it.

But blood is a peculiar substance - like whispers or lies or bad writing, it begets more of itself, and before long everyone is spattered with it. Fortunately, Inspector Barnaby is on hand is to do the clean-up.

That is the joy of the various traditional English detective series spread across BBC Prime and Hallmark - from the exquisite stylings of Agatha Christie's Poirot (Hallmark; Saturdays and Sundays; 18.15pm) to good old Inspector Barnaby of Midsomer (the rural murder capital of the British Isles), there is always, near by, a wise, all-seeing, all-uncovering father figure who will come to town and in due course sweep aside the confusion, bring order to the chaos, uncover the truth.

The detective is not so much a fictional trope as he is a wish-fulfilment. Poirot or Frost or Barnaby or Morse offer to unbelievers what God offers to the faithful: the comfort of the thought that someone will see into the heart of things and set things straight.

In some of the more gloomy episodes, of course, things are set straight altogether too late, but that is in the nature of things. Whenever something needs to be set straight, it is probably already too late.

It is the final outcome that matters, and it is that sense of ultimate reckoning that offers some slight consolation to those caught in the awful here and now. The mills of Morse grind slowly, but they grind exceeding small.

The traditional detective story is more, far more, than morality plays - it is a kind of trench-coated fairy tale, a narrative and mythical balm to the heart, a soothing bedtime fable about a world where that which is hidden is revealed, where the dark of heart receive their come-uppance, where natural justice is finally always served. Poirot! Thou shouldst be living at this hour! We all hath need of thee.