Marivaux wastes no time in exposing the play's artifice. Two women dressed as men rush on to the stage; one bombards the other with a frantic list of questions as to why they're there and what they're doing; and the other supplies everything we need to know about their past and present to set the intricate plot in motion. The what, where and how: the ruling princess Leonide, the daughter of a usurper, has found and fallen in love with the unwitting Agis, the rightful heir to the throne who disappeared as a baby. She wishes to restore his inheritance to him; he has been brought up to hate her. So Leonide has to win his confidence - and heart - from under the noses of his guardians (Hermocrate, a reclusive philosopher, and his spinster sister Leontine) before revealing her real identity. Hence the disguise and her arrival with her servant Corine in Hermocrate's garden.
Leonide's cunning plan demands a breathless feat of role-juggling from Helen McCrory. In order to stay at Hermocrate's retreat and work on Agis, she convinces Leontine (who thinks she's a man) and Hermocrate (who knows she isn't) that he/she is in love with each of them. McCrory relishes the gender-inflected modes of seduction in Martin Crimp's fresh translation, and accentuates the absurdity of flattery. But in between her swift switches from red-blooded male to soft-hearted female, she also finds another register in the aching sincerity of her tremulous dealings with Agis (a gentle Chiwetel Ejiofor). There's a fine line between the telling of lies and the withholding of truths, and though Leonide doesn't so much tread it as sprint along it, McCrory doesn't put a foot wrong.
In James Macdonald's bright, sharp production, the garden bower becomes the centre of a revved-up merry-go-round. The two pawns and one would- be king rush in - to tell Leonide that her unsettling declarations must stop - and rush out, their disciplined exteriors further ruffled by the force of her passion. The stock savant-servant characters revolve like clockwork around them, prompting their masters and lining their pockets.
In comparison to McCrory, the rest of the cast are models of restraint, which is a triumph in itself as Marivaux's characters could easily be played as caricatures. Colin Stinton's Hermocrate has a voice of reason so wearisome that it seems to have bored him into asceticism; as Leonide's assault on his ego intensifies, his imperturbable demeanour is puckered by involuntary twitches of enchantment. Leontine is a figure of fun - if one who has little of it herself. But Linda Bassett's energised performance means that the rollicking release of the joyful schoolgirl trapped inside a schoolmarmish exterior elicits an unexpected surge of sympathy for the losers in Leonide's honourable deception.
At the Beckett Festival Rosaleen Linehan has spent three performances buried up to her waist, then neck in sand. Happy Days places huge demands on a performer's expressiveness, both verbal and facial. Linehan, as Winnie, plumps for the crisp but tired tones of a woman who doesn't want to draw attention to mere trifles - minor ailments, her recalcitrant husband, her inability to move - but whose need to talk gets the better of her. In the first act, Linehan takes delight in the precision of Winnie's just-so rituals; in the second, her anguish that they're now impossible, and the lack of new stimuli, is raw.
The Festival's second triple bill features Act Without Words I - an impish distillation of Beckett's central themes, accompanied by sounds last heard in The Clangers. In the mime, a man's desert existence is dependent on string-pullers, as props are lowered to or whipped from him. What Where is more disturbing and sinister: three dusty men and a loudhailer demonstrate that what goes around, comes around. Again. And again.
The main event - all 15 minutes of it - is Not I, bravely taken on by Niamh Cusack. The manic monologue for a spotlit mouth is best known through the 1982 film, in which the teeth, lips and tongue of Billie Whitelaw fill the screen. So it's a dislocating experience to sit in a blacked- out space, squinting at a pair of lipsticked lips framed within a floating square of light. It's like viewing a penitent through the grille of a huge confessional box, and the expiatory nature of Mouth's narrative stream is further emphasised by the hooded auditor. The ghostly monk-like figure gestures in the shadows when Mouth, four times, denies being the owner of the tumbling life story - "What? Who? No! She!" - and continues in the third person.
But Beckett's original void-like construction has been surpassed by the intensity of the close-up celluloid version. And Cusack's learnt-by-rote delivery - no mean feat in itself - only confirmed why Whitelaw's instinct and intuition made her the playwright's favourite intepreter.
`The Triumph of Love': Almeida, N1 (0171 359 4404), to 25 Sept. Beckett Festival: Barbican, EC2 (0171 638 8891), to Sat