Therese Raquin, National Theatre, London <!-- none onestar twostar threestar fourstar fivestar -->

A love affair with no heart

If you like offal, the French say, you'll like Zola. We may give in to temptation more often than in Zola's day, we may condone sin and even celebrate it, but the sex in his fiction is nothing like the boneless-chicken-breast stuff of our novels and drama. Zola spares his characters nothing. He grinds their noses in the rankness of their acts, bangs their heads against the immovable wall of consequence. But in this adaptation of Zola's first success (1867), the horror is demonstrated rather than felt. This may be a dish of kidneys, but they've been boiled in a bag.

Director Marianne Elliott (who put on the brilliant Pillars of the Community) has several difficult hurdles to jump. One of these, the CinemaScopic breadth of the Lyttelton's stage, is at first managed surprisingly well. This unwieldy setting for an intimate story is converted by Hildegard Bechtler into a sombre flat in which some of the walls have been removed and the remaining ones form a concertina shape to contain the action. There's still quite a desert of stage for the actors to cross, however, and Elliott makes matters worse by opening up a wall at a crucial moment.

Not only does this trivialise the action when nothing horrible is revealed, it is untrue to the spirit of this story of adultery and murder in which the guilty lovers feel, rather, that the walls are closing in, compressing their stink of fear and self-loathing until they can hardly breathe. A bigger obstacle is Nicholas Wright's adaptation, based on a version that Zola himself created. With its emphasis on irony and social comedy, this household seems more English than French.

Camille, the betrayed, blind husband, unwittingly cracks an excellent, Pooterish joke about his friend's attentions to his wife, but the line (and Patrick Kennedy's sprightly performance) make the whining, babyish man of the novel seem homely, almost appealing. The dense, fussy bureaucrat is played by Mark Hadfield with intelligent restraint, but given so much comic business that he takes over any scene in which he appears. The majestic Judy Parfitt is warm and endearing as Camille's doting mother, but this brisk, gracious matron has little in common with Zola's slow but calculating French countrywoman.

Much the greatest problems here, though, are the shape of the play and the casting of the main characters. When the curtain rises, Camille's friend Laurent is already Therese's lover - we don't see the hammer-blow of her introduction to the first vigorous, sensual man in her life, and there is only one hasty and tepid erotic scene.

Charlotte Emmerson is pinched, dazed, and plodding throughout, with a tight, shallow voice that hardly conveys decades of repressed passion, of the resentment that, perhaps more than love, her affair with Laurent gives her the chance to express. Nor is Ben Daniels's suave Laurent at all like the clumsy, impressionable farmer's son of the novel, and the money he will get his hands on when he marries his friend's widow does not, here, come into his decision to kill.

That killing occurs halfway through the first act, in the muffled form of offstage noises while Therese, to the accompaniment of a woman's operatic song, bathes her upper body. This antiseptic, arty treatment is the most striking shortfall between the stage drama and the novel's merciless prose - one that of course didn't exist in the ripely gruesome film versions (the 1981 adaptation, with Kate Nelligan, was terrific).

Too much of the play is then devoted to the couple's disgust, and too much of that is like common domestic bickering. The impression is of a story so adapted to contemporary, local taste that its odd, disturbing flavour has been adapted out of it. This Therese Raquin is easy to swallow, but an hour later you're hungry for a real play.

To 21 February (020-7452 3000; www.nationaltheatre.org.uk)