Last Night's TV - Injustice, ITV1; America's Secret Killers: Dispatches, Channel 4

A few years ago I sat next to Anthony Horowitz at an awards do. He was good company, if a little pleased with himself, and since I'd never heard of him I wasn't sure what he had to be pleased about. That all changed when my sons reached the right age to read his Alex Rider spy novels, which they did, raptly. Then he co-wrote the excellent television drama Collision, which ITV1 ran over five consecutive nights last November. Now the channel has indulged him again, doing the same thing with Injustice, which he wrote, I assume on his own this time, and executive-produced. I'd say he's entitled to feel pleased with himself.

Collision, you might recall, used a fatal road accident to connect a number of people with lives in varying states of complication. I don't know to what extent Horowitz and his co-writer were inspired by the brilliant and similarly plotted 2004 film Crash, but anyway they generated as much compelling drama from a stretch of the A12 in Essex as Paul Haggis, the writer-director of Crash, did from a Los Angeles freeway. This time, Horowitz ventures further up the A12, to Suffolk, where barrister Will Travers (James Purefoy) has settled with his wife, Jane (Dervla Kirwan), and children, after seemingly suffering some kind of nervous breakdown in London.

Many of the devices we saw in Collision are used again, not least creative use of the flashback. The story began with Travers defending a young man accused of robbing a war veteran, and the evidence of a security guard, one of the prosecution's key witnesses, was at first backed up by the flashback we saw of the defendant walking clearly into the light of a streetlamp. In court, however, it emerged that the lamp hadn't been working that night, cue another flashback, in which all was dark and shadowy, conditions in which the security guard couldn't possibly have identified the accused man. So, from this tantalising device we know that a much more significant flashback, in which Travers shot dead an itinerant farmworker he had followed to a remote cottage, just might be leading us up the garden path and round the ornamental pond.

Plainly, though, Travers knew the farmworker, having spotted him, to his manifest concern, on the opposite platform at Ipswich station. Horowitz's skill as a scriptwriter is to weave together disparate characters and storylines. Thus, we don't yet know how a budding writer in a young offenders' institution, where Jane Travers takes reading classes, will engage with the main story, which now has Travers agreeing to represent his wife's ex-boyfriend, an old university pal accused of murdering the secretary with whom he was having an affair.

I should think that most people who watched last night's opener will want to see how all this unfolds over the course of the week, which is what ITV1 is banking on. Certainly, the thing is helped along by strong direction (Colm McCarthy, using but not overdoing the tricks of his trade, such as slow-mo) and genuinely classy acting. The ever-excellent Purefoy makes a convincing job of the enigmatic Travers, alternately in firm control of his life and on the edge of instability. And there is a powerful turn by Charlie Creed-Miles as an efficient but unsavoury detective, who in the way of unsavoury detectives everywhere (on telly if not in life), takes sadistic pleasure in exposing his inexperienced sidekick to the gruesome realities of a murder investigation.

As for Jane, Kirwan is her usual lovely, watchable self, so lovely, so watchable, and so apparently guileless that I wonder whether hers might have been the finger on the trigger.

There is no such uncertainty in Afghanistan, where the escalating "kill-capture" policy toward even mid-ranking Taliban leaders can be traced directly to the commander of the US forces, General David Petraeus. It was a coup for Dan Edge, who made America's Secret Killers: Dispatches, to land an interview with Petraeus, yet rather more of a coup to bag an interview with a regional Taliban commander, who made the predictable but nevertheless blood-chilling forecast that as many militants as the US and its allies kill, so the dead will in turn be avenged by their children.

Apart from his unsettling habit of swearing eternal and deadly enmity towards the infidel, he seemed like an ordinary, almost decent sort of fellow, this Afghan; handsome, eloquent, and dressed in a combination of fatigues and scarves that are either already marketed as Taliban chic, or very soon will be. Whatever, it's never a bad thing to hear the other side's point of view, and while Edge's film, and the thrust of reporter Stephen Grey's questions, will no doubt be dismissed as pinko propaganda by supporters of the US initiative to kill first and ask questions later, his contribution underlined the validity of the central poser: are we creating more insurgents than we are killing?

Edge and Grey nailed their colours, pinko or otherwise, fairly firmly to the mast, showing a tribal leader on the side of the government questioning his allegiance after being dragged off for questioning by US soldiers, and finding "compelling" evidence that the victim of one targeted assassination was a victim of misidentification. Since an American bomb had blown this man and everyone else in his car to smithereens, nobody quite knows who he was. General Petraeus insisted that he was satisfied that the right person had been eliminated, but then he would, wouldn't he?