Dr Jeffery Wigand (Russell Crowe) had more reason than most to be nervous of giving up tobacco. Like e-mail death threats and a bullet in the mail. Ostensibly let go for "poor communication skills" from a senior position at cigarette giant Brown & Williamson, Wigand went on to demonstrate his verbal dexterity in a taboo-busting interview with the respected 60 Minutes, fronted by the redoubtable Mike Wallace (a formidable Christopher Plummer). Enticed to breach his own confidentiality agreement and reveal his erstwhile employer's sharp practice by producer Lowell Bergman (Al Pacino, excellent), Wigand's world collapses. He is forced to sell his luxurious home and, later, move into a hotel when his wife leaves with the kids. His descent is only complete, however, once CBS corporate pressure forces the show to pull his segment.

If the events in Michael Mann's Heat follow-up nudge us toward cinema's 70s heyday (All The President's Men and The China Syndrome are obvious touchstones), then the comparison is not invidious. There is something slightly grubby about this tale of little men and powerful companies. The halting Wigand was not a conventional hero, and his eventual breaking of cover seems to have at least as much to do with personal vendetta as any imperative to Do The Right Thing. Having him played by Russell Crowe, L.A. Confidential's lithe psycho cop, might appear on paper to invest Wigand with some physical charisma, until you realise that the actor has bulked-up and adopted grey hair for the occasion. It's award-worthy performance.

The Fourth Estate is hardly covered in Woodward and Bernstein-style glory either. Pacino's Bergman is largely honourable, but too often the media are bound as much to commercial concerns as hard news. There is nothing self-congratulatory about the film; The Insider has plenty of villains and very few heroes. Nor is it a film about smoking. One senses that Mann fastened on Wigand's story (apart from a little dramatic telescoping, this is all essentially true) not because he had a particular axe to grind against Big Tabacco (he's a smoker himself), but because it provides the perfect backdrop to talk about honesty and loyalty and honour. The end, too, is rare in Hollywood terms for the way in which it subtly drags defeat from the jaws of victory. No one in the picture smokes.

Under the unwavering gaze of Dante Spinotti's camera, the film looks gorgeous, even for a director possessed of Mann's pronounced visual literacy. Largely absent is the hard-edged architectural cinema of Heat or Manhunter, in its place are a sickly hand-held blue/sea-green palette and, startlingly for a film realised so comprehensively in widescreen, an intense use of close-up. This is a film whose paranoid aura is as much about texture and grain as the big picture. Lisa Gerrard and Pieter Bourke's muscular soundtrack is a constant delight.

The Insider, like Heat, is a violent film, except that it internalises its aggression; battles are fought with words. We can define its method as 'adult' if only because it's a film where people do little more than talk - a simple skill all too easily forgotten. More sombre, less flamboyant than his previous work, time might just prove this highly addictive feature to be the remarkable Michael Mann at his very best.