24 BBC2

In 24, it is not only the secure phones that are scrambled. With its false leads, double-crosses and triple-bluffs, the story has whisked many viewers, not to mention protagonists, into a state of delicious confusion.

If Nina is the traitor, why did the bad guys instruct Jack to kill her? Why did she inform Teri that Alan wasn't really Alan? Come to that, why didn't Alan just kidnap Teri straight away, instead of waiting until she found out that he wasn't Alan? And why does everyone have such good cheekbones?

A first-rate thriller can withstand a few superfluous twists. The Big Sleep famously contained an entire subplot that not even its author, Raymond Chandler, could explain. But 24 is different: it ticks with teleological purpose. The ingenious use of 'real time' (in which each of the 24 episodes represents an hour of unfolding events), the intricate plotting and primed-bomb tension all along have pointed to a neat resolution.

Now, with just one episode to go, and doubtless a second series in mind, that no longer appears likely. Short of a last-minute intervention by a hound named Scooby, the loose ends seem destined to remain flagrantly untied. But let's not get anal before we reach the story's bottom.

Just 23 hours ago (although it seems more like six months), Jack Bauer (Kiefer Sutherland), of the Los Angeles Counter Terrorist Unit, was sitting at home scrutinising a chess board. His next move has still to be played because, at the stroke of midnight, his opponent and daughter, Kimberly (Elisha Cuthbert), was lured away into the darkness. His skills as a strategist, however, are put to exhaustive use in what he calls, without exaggeration, the longest day of his life.

To begin with, Kimberly is abducted, held hostage, threatened with rape, subjected to a near-execution and rescued in a shoot-out. Later, she escapes from another kidnap attempt, but is mistakenly arrested in a drugs sting. Once released she is recaptured. In the course of her day she witnesses at least five murders, and, for most of it, is forced to wear a skimpy, if rather fetching, red top. Yet such is the narrative richness of 24 that Kim's travails have often seemed like a trifling sideshow.

Right after his daughter's disappearance, Bauer learns of a plan to assassinate a black presidential candidate, Senator David Palmer (Dennis Haysbert), as well as a conspiracy at the heart of the secret services. Subsequently his boss is shot dead in front of him, although not before issuing the warning: 'Don't trust anybody.'

Sound advice, indeed. Not since the mid-Seventies, and films such as The Parallax View and The Conversation, has paranoia seemed so sensible. Nor has night-time LA ever looked more sinister. Under the glare of a restless camera, the empty suburbs almost shimmer with malevolent intent.

Bauer patrols vacant offices, long-silent corridors and depopulated streets in pursuit of a truth that is seemingly just beyond his grasp. While everyone else in the secret services travels in a black-suited retinue, Jack is a free spirit in a T-shirt, and something of a loner. Nevertheless, he is constantly plugged into a digital support system of mobile communications, swipe cards, surveillance cameras and satellite images. That's the thing about contemporary isolation: you never have to be alone.

If Bauer is the modern version of Chandler's hero - neither tarnished nor afraid - then 24, with its shadowy sets and keyboard cops, works as a kind of nerd-noir. Instead of cigarettes, Bauer, like everyone else, carries a mobile phone. And while no one is shy about using a gun, the weapon of choice is a computer rather than a Colt 45. Breaking heads is now secondary to breaking codes.

The underlying irony, of course, is that while Bauer is hooked up to the world, he finds it difficult to communicate with his wife. Not long ago they separated following a lugubrious period when Bauer returned from a secret mission in Belgrade. Although the couple are reunited, it's not until Teri (Leslie Hope) is also kidnapped that her husband finds the right words, which are, essentially, don't worry, I'm coming to save you.

At the centre of 24, surrounded by international intrigue, is a domestic tale of two high-achieving families - the Bauers and the Palmers - placed under intolerable pressure. The stress, alas, is routinely treated with a syrupy dose of sentiment - the series features more 'I love you's than an early Beatles album.

Even so, and unusually for an action drama, the role of the two wives is pivotal. Sherry Palmer (Penny Johnson Jerald) is a woman whose livid ambition makes Lady Macbeth look like some loved-up hippy in a flowing dress. She has her work cut out with her husband, who acts as if he's only just accepted that Santa Claus doesn't exist. Still, with a woman like that pulling the strings, anyone could become President.

Teri, on the other hand, is a study in unspoken disappointment and indestructible elegance. It is a generous performance from Hope, which allows the other characters space in which to manoeuvre; and Nina (Sarah Clarke), Jack's assistant and former lover, wisely uses it to explore her sashay. She may appear to keep her lips sealed, but there is nothing the poor girl can do to prevent her hips from making a full statement. Nina can turn a dash to the loo into a stroll along a Paris catwalk.

Most of the Bauers' and the Palmers' problems can be traced, via Jack's Belgrade mission, to a third family, the Drazens, a trio of homicidal Serbs. But it should also be said that most of 24's problems can be traced to the same source.

For the first 12 episodes, the series successfully tethered political fantasy to suburban realism. While exploding jumbo-jets and beautiful lesbian assassins stretched credibility to its pleasurable limits, the authentic dialogue of familial disputes and office feuds brought us knowingly back to earth.

In this manner, the progression towards a climax is slickly controlled. Thus the dead-eyed punk who abducts Kimberly and is a dab hand with a crowbar is properly menacing - though not nearly as menacing as Gaines, the icy crime boss who kills him without a first, let alone a second, thought.

But as ruthless as Gaines is, he is still shot dead by Jack at the halfway point, which means the next bad guy in the conspiracy has to be even badder. Alexis Drazen doesn't look bad. He looks good, too good. In a show in which patrol cops, junkies and even air hostesses are physically stunning (and when did you last see a head-turning air hostess?), Alexis stands out with his magazine-model appearance. And although we see him kill a lot of people, the only anxiety he produces stems from the suspicion that he is probably running late for a Calvin Klein underwear commercial.

For all his eastern European abruptness and readiness to slot the first person to give him a funny look, Alexis's brother, Andre, is no more unnerving. That leaves their father, Victor, the ethnic cleanser and all-round madman who lays claim to the title of the baddest of 24's baddies. Victor is apparently the mastermind behind the plot to kill Palmer, Bauer and Bauer's family. Half-man, half-monster, he is held captive, like some modern-day Minotaur, in a secret underground labyrinth. We first see him with a sack over his head. The disappointment I experienced when the bag was removed reminded me of the comedown I felt as a child at the moment in The Wizard of Oz when the curtain is pulled back to reveal dotty old Frank Morgan as the Wizard. It was Frank all over again; Frank from Blue Velvet, that is, otherwise known as Dennis Hopper.

One of the many joys of 24 has been the textured performances given by largely unknown actors. Even Sutherland, the nominal star and major revelation, was a certified has-been (working as a rodeo rider). His haunted, sleepless features are showing signs of the same appealing scepticism that made his father so watchable. It is not easy to make moral decency look interesting, but Sutherland is never less than compelling.

By the same token, it should be hard to make depravity look dull. Hard, but not beyond Hopper. His cartoonish, raised-shoulders psycho-act has become tiresomely familiar. The only novelty is his attempt at a Balkan accent. The guiding principle seems to be that, when in doubt, add an extra two syllables to a word. It is the closest 24 comes to a joke. With the possible exception of the Vicar of Dibley, this series could prove to be the longest-ever stretch of television in which nobody makes an effort to be funny. Such is the extraordinary pace and inspired editing that levity has simply not been required.

That sustained suspense, I fear, has had a similar effect on viewers as it had on Teri. 'I think,' said her doctor friend, 'you've got a condition called disassociative amnesia. We need to get you home.'

For those of us who can't remember life before 24, finding our way back is going to take a little time.