End of the trail for Sarah Lund and The Killing

The Killing III came to a bloody and somewhat bewildering end last night, Sarah Lund perhaps taking the show's title too literally and jetting off to yet more darkness. As she disappeared into oblivion, so the curtain came down on one of the most talked-about, boxset-friendly cultural landmarks of the 21st century to date.

The Danish noir debuted on BBC Four only 18 months ago, but quickly attained cult status through word of mouth and rhapsodic broadsheet reverence. Its largely middle-class audience obsessed over plot twists and tongue-twisting Danish names ("Troels!"), and discovered a hitherto untapped, if ironic, appreciation for chunky knitwear. And now it's all over. Twitter will be quieter with its passing.

Much of this final series provided a fitting denouement for such a mesmerising show, but it also revealed that, after just three series, its makers were rather running out of ideas. After The Killing II included an unlikely segue into Afghanistan, this series deposited Lund (played to customary perfection by Sofie Grabol) back into familiar territory: investigating another family wrenched apart by the loss of a daughter in her typically dogged manner, which once again, brought her into conflict with her superiors, and had political leaders wanting her banished to Norway at the very least.

But to its credit, III did at least try to introduce a softer, more humane side to a lead character with fewer facial expressions than Frankenstein's monster, and every bit as compelling. Here, we saw Lund with her hair down, in heels, and out of knitwear; we even saw the cleft in her bare buttocks as she rose post-coitally from a crumpled bed. And if that weren't discombobulating enough, there was suggestion of her reuniting with her estranged son, and settling into contented grandmotherhood.

It couldn't last, and duly didn't. Lund was helplessly drawn back into the case of a kidnapped girl, a case with tentacles leading into politics and business, and down an awful lot of dark alleys. But last night's climax disappointed because it had Lund do what the Sarah Lund of the previous 39 episodes would never have done: take leave of her senses. But then perhaps that's what a perpetually overcast Copenhagen does to the soul. Much as her overused torch was likely running out of batteries, so too was the poor woman herself, and so she went out in a blaze of glory, albeit Scandinavian-style: at night, with stealth, and on her face the full realisation of what her actions would mean for the rest of her wretched life.

Devoted viewers may have craved a more satisfying ending, but they'd be fools to have expected a happier one. The Killing, after all, never offered comfort to anyone.

It's right and proper that the makers end it here. Television history tells us that this level of quality rarely endures, so let the US rema ke of The Killing continue to dilute its power with endless series. In its gaping absence, we'll gorge on whatever BBC Four offers in its place: The Bridge, for instance, and Borgen (which returns to our screens next month) are similarly accomplished – and Danish. What better pedigree?

Short and sweet

The old adage that you should always leave your audience wanting more has been proved by some of the best TV shows. Fawlty Towers followed the advice to the letter when it closed its doors for the last time after only two series – three years apart – and 12 episodes.

Three decades later, Ricky Gervais and Stephen Merchant trod the same path with The Office, albeit with two Christmas specials added to its dozen episodes. David Lynch's Twin Peaks proved uncharacteristic for an American show in this respect. Instead of signing its stars to multiple seasons, the cult mystery drama also ended before it had outstayed its welcome. Eight first-series episodes were followed by the longer second series of 22.

Kiwi comedy-folk duo Jemaine Clement and Bret McKenzie packed away their guitars after just two series of Flight of the Conchords. It should never have worked, but with musical lines such as "I'm not crying, it's just been raining on my face", it did.