When the actor-director pairing’s wrong, we end up with cardboard characters like Colin Farrell’s lugubrious Sonny Crockett in Miami Vice. Mann’s latest film – his first as director since Public Enemies in 2009 – is an intense thriller with a premise ripped straight from the headlines but hobbled by banal dialogue and two-dimensional characters. When a hack on a Chinese nuclear power station results in a devastating meltdown, and a further cyber assault on the stock market causes havoc with the price of soy, computer genius Hathaway (Hemsworth) is taken out of prison to help track down the culprit. Together with the FBI (represented by Viola Davis’s no-nonsense Carol Barrett) and the Chinese government – step forward brother-and-sister cyber experts Chen Dawai (Leehorn Wang) and Chen Lien (Wei Tang) – Hathaway’s investigations lead him from America to Asia, where a shadowy villain lurks behind a tangled web of proxy servers, remote transmitters and false identities. Mann brings an almost seductive air to the otherwise dry world of hacking, with lingering shots of Hemsworth typing with his shirt unbuttoned to the navel, USB sticks slowly interfacing with shiny ports, and characters murmuring about packet sniffing. But the action sequences are Blackhat’s strongest aspect – and Mann can still stage a fist-fight or gun battle as well as any director currently working. It’s in the scenes of dialogue, indifferently scripted by Morgan Davis Foehl (Click, I Now Pronounce You Chuck & Larry), that Blackhat descends into the murk. Hemsworth’s relationship with Wei Tang is the weakest romance in Mann’s career; to say they lack a sense of chemistry is an understatement – at times, it feels as though they’re not even in the same room as each other. Hemsworth doesn’t seem to know quite what to do with his terse, ultra-masculine genius of a character. Like Frank in Thief, Hathaway’s as smart as he’s tough; like Manhunter’s Will Graham, he’s on a personal mission to catch a man he’s never met; like Hawkeye in The Last Of The Mohicans, he’s adept at using a variety of weapons. Unfortunately, Hemsworth’s handling of Hathaway doesn’t resemble any of these characters as much as Brian O’Conner out of the Fast & Furious franchise. Confident when he has to rapidly tap at a keyboard and handy in a fight, Hemsworth draws a blank when he has to invest his character with emotional depth. Mann’s camera tracks his face as he stares out of a window, but we can read nothing from his eyes. The problem, perhaps, is that Hemsworth isn’t given anything dramatically meaty to play with: Hathaway is such an improbably gallant and fearless man that he somehow seems even less like an ordinary mortal than Thor. Collected though Neil Macaulay, Hawkeye or Will Graham were, we constantly felt as though their lives had a scope beyond what we saw on the screen: they had regrets, mental scars, disappointments that hung over them like a cloud. The only thing hanging over Hathaway is his beautifully-styled hair. Of the supporting cast, only Viola Davis manages to invest her character with any sense of purpose or edge. While everyone else coasts by on cool poses and smouldering expressions, Davis works her dialogue for all it’s worth, turning an otherwise stock FBI agent into someone dynamic and worth rooting for. Blackhat may have been more successful if Mann had changed the habit of a lifetime and cast Davis as the protagonist instead. It’s a distinctive and even oppressive look, furthered by sound design which bathes us in the deafening roar of gunshots and the grind of huge machines in motion. Even the rattle of keys on a keyboard take on a cacophonous quality. Oddly, there are minor problems even here: dialogue frequently changes volume and even appears to fall out of synch, hinting at either last-minute additions to the script or perhaps a film being rushed to completion. In terms of plot, Blackhat is a similarly awkward amalgam. Its opening third points to a muted, intelligent drama-thriller with the same level of real-world detail as The Insider, but no sooner has Hathaway emerged from prison and caused Chen Lien to go all weak at the knees with a single blue steel stare than the film descends into more familiar thriller territory. All of this might make Blackhat sound like a complete disaster, and early reviews from the US have been largely damning. But while it’s true that Blackhat is several league tables below Mann’s very best work, it’s still entertaining enough when taken in isolation as a slick, icy genre film. Even its poker-faced tone adds to the fun; it’s strangely entertaining, for example, to observe Wei Tang’s performance, where she’s often given so little to do that she just looks around at the windows and wall fittings. Given the implications raised by the recent Sony hacks, Blackhat is something of a missed opportunity. The notion of a hacker triggering a nuclear meltdown is a terrifying one, but beyond a couple of well-handled set-pieces, Mann somehow fails to make the implications of this kind of power really land home. What could have been a far more powerful insight into the precarious nature of a world entirely reliant on computers instead becomes a vehicle for Hemsworth, who emerges here as a kind of MacGyver for the 21st century: a hit with ladies, and as handy with a lathe as he is with a computer terminal. That Blackhat emerges as a diverting thriller is some comfort, and the film comes cautiously recommended for the quality of Mann’s direction alone. That he hasn’t managed to forge a post-millennial, web-enabled Heat 2.0 is nevertheless a disappointment. Follow our Twitter feed for faster news and bad jokes right here. And be our Facebook chum here.