uwantme2killhim?

Mark has a girlfriend. Well, technically two - he's sleeping with Zoey whose other boyfriend wants to join the army, and he's sufficiently passionate about Rachel that he attempts to chat to her online post-coitally. Rachel's on the internet. Resembling the kind of anecdote that fills The Law Of The Playground, Mark's girlfriend Rachel can't visit, can't be visited - she's in witness protection.

Most of the relationships around Mark would be marked "It's Complicated", but we're set back in 2003. There are social networks, but they're ones now extinct - your sort of pre-Zuckerberg pre-Cambrian, all weird spiny creatures like Friendster, or survivors maintained in little niches that once stretched to the horizon, AOL and MySpace as ferns or trilobites surviving in isolated valleys in Australasia. 2003, with pay as you go mobile phones in teenagers' pockets, picture messaging on flip-phones and desktop computers, 2003 when everybody's username had a year in it, 2003 when a boy decides to kill someone over the internet and does so.

There's a discussion about probability that's one of those troubled-relationship indicators, the whole "idiot tax", "more chance of being hit be a meteorite" - as it's observed, perhaps a bit too neatly, that every week in the papers you read about people winning the lottery, but you never hear about people being hit by a rock from space. The film's aware that it's an improbable story, so it does everything in its power to couch it as being based on a true story, but for all that it's ironically unconvincing.

The technical details are there, alright. A police station in London would probably have used some of that anti-terrorism cash to buy a laser printer, but dot-matrix says "olden times" in a way that will dishearten anyone in their thirties. As most of the motivating action takes place online, the film's approach to representing it is vital - unfortunately, it seems to have taken a lesson from the Carrie Bradshaw school of screenwriting. Alone in front of their screens, it's apparently only natural that people read out what they're typing.

Representing one communication medium in another can be a difficult business, but there's surely a better way to do it than this. It feels clumsier than listening to Keanu Reeves' turn in Dracula as an epistolary railway sleeper. It might be a reference to the way that Sex & The City represented the process of writing an advice column; the TV show was approximately contemporaneous, but it's more likely a lack of imagination. While we can assume that what we're seeing is what Mark does, and it's careful to relate what he's seeing with what's going on elsewhere, there's not enough done to justify his romantic optimism.

While Jamie Blackley is good as Mark, and Toby Regbo is equally good as his troubled pal John, they are let down by everything except the surrounding performances. Mark Womack and Louise Delamere don't have much to do as Mark's parents, but they do it well - Jaime Winstone is sultry and seductive as Rachel; Joanne Froggatt as the investigating officer manages a neat mixture of concern and control, efficiency and exasperation. It's just that the film relies so much on the fact that it's based on a true story that it fails to do anything else to be believable.

We're never given a solid reason for Mark's credulity, nor evidence of it elsewhere. His relationship with Rachel is the centre of the film but it's never clear how they met. When her superiors ask her why it matters why Mark decided to murder she doesn't mention paedophilia - indeed, if you've got a doomed romance that ends in bloodshed set in a London comprehensive why wouldn't you make mention of Romeo & Juliet? In this case a reference that cliched might have helped, because the film's other touchstones feel as hackneyed.

There's an array of production companies behind "u want me 2 kill him?", among them usual suspects like the Weinsteins and the actual producers of The Usual Suspects - perhaps that's why one revelatory montage feels like Keyser Soze's storytelling. Like Die Hard 4.0 it's about the internet and based on an article, admittedly one in Vanity Fair rather than Wired, so you'd expect it to be longer on human interest than technical detail. That just makes it all the more galling that for all the effort put into graphics and such, the motivations and emotions behind it feel flat, trite, and under-represented. There's no point in complaining about the absence of dialup noises or an ADSL modem that isn't connected to a master socket when a film leaves you failing to believe a true story.

It's weird to hear current indie sensation Jake Bugg on the soundtrack for a film that's set when Mr Bugg was nine years old. Jon Hopkins (who scored Gareth Edward's Monsters) provides the score - it's good, but musical cues tend not to help create a sense of reality. This is a debut feature for screenwriter Mike Walden, and while producer Judy Bachrach wrote the original article she's not credited behind a typewriter here. Andrew Douglas directed the 2005 Amityville Horror, and is relatively capable here - though with this many producers (five are credited in the publicity bumpf) it's hard to know how many hands were stirring the pot. While some bits are interestingly staged, you're online right now - you know the score - do you consider people inducing others to kill as one of "the hidden evils that lurk deep within the internet" or are you more worried about somebody dressed up as a school?

It's unfortunate that there are so many big stories breaking about the way we use and are observed on the Internet, because uwantme2killhim? can't stand up to scrutiny. Some movies are improved by seeing how they build towards their ending once you know it, but this isn't one of them - it might be a retelling of a true story, but you wouldn't want to watch it twice. Indeed, you're probably as well not watching it at all.