The well-worn subject of corporate irresponsibility uncovered by one man’s brave defection is somewhat muddied by a pretentious subplot in Tony Gilroy’s otherwise impressive directing debut.

The title name is as eloquent as that of the fictional Willy Loman, product of the competitive corporate world of forty years ago. Like him, Michael Clayton, (George Clooney) half brightest star and half flawed human, struggles in a setting where reality crushed youthful idealism a long time ago. ‘I am Shiva, god of death’ announces Michael’s lawyer colleague, the deranged Aden Eden, played to the apocalyptic hilt by a shambling Tom Wilkinson. Touching pitch has left him defiled, or as he puts it, ‘covered in a patina of shit’. After six years spent defending a class action against agrochemical company U/North he’s stopped taking the medication. Metaphorically and literally, he refuses to hide the truth any longer.

Tony Gilroy’s dialogue shows the flair that enlivened the first two films of the Jason Bourne’ trilogy and he has the knack of engaging an audience’s attention as he steers his hero through a number of fraught situations. However, an extraneous plot strand about a coded text, a storyline that treats males as human beings but women as troublesome ciphers and some implausible actions are flaws in a generally engaging thriller.

Michael Clayton has a lot to contend with besides the demands of his job as ‘fixer’ for a top New York legal firm. Short notice calls to handle minor but urgent cases are his stock in trade. They add to his already edgy melancholy, resulting from a failed business venture and a serious gambling habit which have left him with heavy debts. He is a woefully inadequate divorced parent, mostly spending his access time with his son driving between jobs. On the brink of quitting, he’s persuaded by boss, Marty Bach (Sydney Pollack), a stern but compassionate father-figure, to stay. After seventeen years with the company he should have made partner but Marty tells him nobody could do the job as well as him.

Michael agrees to find Aden, an old friend, when he goes missing after abandoning the defence case. Marty underlines the urgency, reminding him that they could incur huge compensation costs if the company Aden’s supposed to represent loses the case. Michael calls on the same reserves of loyalty that has him eating out of Marty’s hand and comes up against ruthless top lawyer Karen Crowder (Tilda Swinton) and her henchmen. The sinister pair, mostly ensconced in their surveillance vehicle, are willing to do ‘what it takes’ to ensure a good result. Arthur has disappeared with a document proving U/North knowingly released a deadly poison into a local water supply.

The low-key action in moody settings is played out against a subtle soundtrack, punctuated by sudden, quickly resolved activity. There is a particularly slick and soundless assassination scene. However, complexity shades into messy confusion at times. Children in the thriller genre make the hero vulnerable to threats by the bad guys, but here a side plot into 'Da Vinci Code'/ 'Harry Potter' territory, linked to Aden's delusions, is confusing. The same may be said of Aden’s slightly suspect relationship with one of the eco-damage victims.

A car-chase almost masks the unlikeliness of the climax. Michael, prone to statements like ‘I’m not a miracle-worker, I’m a janitor’ and more at ease in a cellar with a diminishing pile of poker chips than among green fields, leaves his car after escaping the bad guys to commune with horses on a hillside. What happens next may not be a miracle but it must rank one of the luckiest breaks on film. As if to test our credibility, the director shows the same mawkish incident and its aftermath twice over, once at the start of the film and again at the end of a long flash-back.

The role of Karen, saved from caricature only by Tilda Swinton’s acting, is another flaw which may go un-noticed in the general hurly-burly of a film genre which targets males. Typically seen practising her deposition speech and worrying about sweat stains on her shirt or fussing over her clothes, her uncertainty contrasts with the hero’s crumpled confidence. Of course, she has a lot to sweat about, given the stakes, but this is before she unilaterally decides to eliminate the opposition. If Michael’s slumped shoulders bear the weight of his extended-family problems and loveable character weaknesses, Karen’s willingness to lay her career and even her freedom on the line for U/North is inexplicable. For unmotivated evil, the part comes little short of her 2005 role as White Witch in ‘The Lion, the Witch and the Wardrobe’. Michael’s and Aden’s back-stories are lavishly constructed compared with that of their female opponent.

Michel’s final act of quick-thinking opportunism gives a satisfying twist which promises a happy ending. However, the ambiguous long take of the final scene, a close up of Michael’s face in a taxi after his instruction to ‘Just drive!’, has the same tinge of disappointment, if not the desperation, that was there at the start of the movie. Forty years on from ‘Death of a Salesman’, the lesson for the ‘low-man’ is much the same.