On a flight from Tokyo to Paris, one first-class passenger surreptitiously drugs the water of another. When that drugged business executive begins to pass out at the airport, she is picked up by two men who throw her into the boot of her own car and steal the briefcase that was hand-cuffed to her wrist. It is all a day in the life of corporate espionage.

Olivier Assayas’ 2002 thriller Demonlover depicts a highly competitive world of corporate business, cut-throat executives, and pornography. It tracks a French media corporation negotiating to buy up an exclusive license to some of Japan’s most popular pornographic anime and manga – known as ‘entail’ – and thus leave its European competitors in the dust. Diane de Monx (Connie Nielsen) is placed in charge of the deal when the original head – the woman drugged on a plane – is taken out of the action, but it soon becomes clear that Diane may not be working for her employer at all.

Demonlover is a difficult film, showing considerably more potential than actual quality. It faced mixed reviews upon release, has more recently developed into something of a cult favourite, and is sporadically claimed by critics to form part of France’s contentious ‘New French Extremity’ movement. Its inclusion there is rather tenuous; it deals with provocative subject matters and gets comparatively more extreme as it develops, but there is nothing to rank alongside the contention that followed the likes of Irreversible, Romance, or Martyrs. The first hour or so is genuinely great, and depicts a winner-takes-all struggle in which everyone is seeking not just their own success but their rivals’ failure. Its corporate setting, technological focus, and gaudy – if not downright racist – exploitation of Japanese culture lead the film to seem a present-day work of cyberpunk. Sadly Assayas loses his way in the film’s last half-hour or so, both as a screenwriter and as a director. By the end Demonlover has collapsed in on itself into something of a mess, its story collapsed and all sense of coherence largely removed. It is two-thirds of a good film stapled to one-third of a bad one.

It is a deep shame that it ends in such a fashion, since for so long it seems such a distinctive and effective thriller. The performances are excellent, particularly by Connie Nielsen in the central role of Diane. Assayas’ script affords her the chance to build a character of different motivations and emotions, and a powerful sense of strength. American actor Chloe Sevigny plays executive assistant Elise in a manner that begins simple but gains in complexity as she goes. Charles Berling is pitch-perfect as the sleazy and instinctively untrustworthy colleague Hervé. There is a sense of stunt casting in the brief appearance by Gina Gershon (Bound, Showgirls) as boss of a leading adult Internet provider, but if so it is a stunt well-played. The cast are in top-form and fully commit, which makes it such a shame that it is all destined to collapse before the closing credits roll.

There is plenty of good in Demonlover, but is it a good film? That is something much harder to justify. This is a lost opportunity.