SPOILER alert: if you watched the recent TV crime drama The Fall, but missed the final episode, look away now. If you did not watch The Fall, feel free to proceed. Prior knowledge is not essential for the enjoyment of this piece.

The BBC2 drama was a success with everyone, until the end, when everyone got angry. It did not have a happy ending, you see, and many thought that that was the least they deserved, after the scenes they had witnessed on screen.

The story is simple: a young attractive male, a family man, attacks and murders young attractive women. But we witness the horror of the assaults without the reassuring denouement of capture; for, in The Fall, the killer evades justice and gets away - with the police some distance behind. And, as the final credits rolled, the nation was furious, more shocked by this than the murders themselves.

So, was the writer of the programme, Allan Cubitt, surprised at the reaction? He expected "that the ending would divide people", he says, "possibly frustrating those who like things neatly sewn up. But I also thought that there would be people who would find it exciting, and truer to the nature of such crimes and the attendant police work." And, in a way, it is.

Most women who are murdered are killed by someone known to them. On average, two women a week are killed in the UK by a violent partner or ex-partner - which comprises nearly 40 per cent of all female murders. Such crimes are quickly solved by the police, usually within 48 hours. But "strange murders", as Cubitt calls them, are a great deal harder. "To that degree," he says, "given the commission was for five parts, I felt it was the only ending the series could have."

Hardly: Marple, Poirot, and Morse do not need five parts; with them, everything is sorted out within a couple of hours. But Cubitt is uncomfortable with happy endings. "Episodic TV has to wrap things up in an hour, which never seems very real. More usual, with a longer-running series, is a bitter-sweet ending: the bad person is defeated, but the lead police officer has to do some soul-searching as a result of the things they've done to nail the perpetrator. It's hard to make such endings genuinely cathartic."

I am reminded of Goethe asking preachers not to share their doubts because he had enough of his own; with so much in our lives unresolved, we do not need crime dramas to add to the list: we want resolution. I suspect, however, that Cubitt feels a sneaking guilt, holding out a tantalising promise: "I probably robbed the Fall audience of their catharsis, but I hope they'll come back for more in season two."

Ah, there's a sequel. But do we catharsis junkies risk it?

Simon Parke is the author of A Vicar, Crucified (DLT, 2013).