DU MAURIER was a master manipulator, sowing nagging doubt with a single line and leading readers by the nose from one rash conclusion to the next, only to pull the rug at the eleventh hour.

Joseph O’Connor’s deliciously ambiguous adaptation of her psychological thriller, My Cousin Rachel, certainly does the deft thimblerigger justice.

Is Rachel a temptress, murderer, con artist – a wicked amalgam of all of the above – or merely a vulnerable and deeply misunderstood woman intent on survival? Alluring, carefree and unconventional, Countess Rachel Sangalletti travels from Florence to the Ashley estate in Cornwall, home of her recently deceased husband Ambrose and now helmed by his ward and heir Philip. Convinced she murdered Ambrose – gripped by paranoia, in his finals days his feverish guardian penned a series of letters accusing his wife of poisoning him and left her out of his will – young Philip wows to get vengeance on the ‘black widow’. Soon, however, like every man lucky (or unlucky?) enough to cross her path, he falls under the enigmatic femme fatale’s spell, accepting her version of events (backed by a conclusive post-mortem): Ambrose succumbed to brain tumour like his father and grandfather before him.

Hopelessly smitten, Philip not only lavishes a reticent Rachel with gifts in a bid to ease his conscience and make amends but offers her a generous allowance – which the proud widow pointedly refuses before grudgingly accepting.

Was this all part of her Machiavellian plan to claim her share of the Ashley fortune or is Philip’s largesse simply out of her control? And is the irrepressible sexual tension between the pair her doing or a figment of Philip’s imagination?

Helen George is utterly mesmerising as Rachel. Although clearly manipulative on some level – Rachel is twice widowed and like most women of her class, has had to pander to men and trade on her ravaging looks to make her way in the world – her manipulations feel more intuitive, a force of habit, than conniving.

Steering clear of more overtly sexual and sexualised interpretations (Rachel Weisz in Roger Michell’s 2017 film adaptation springs to mind) she imbues the widow with refreshing depth – in line with Du Maurier’s original – making us question our readiness to believe half-truths and side with an increasingly unhinged Philip.

Jack Holden is her match in every way as the naïve and rather stroppy Philip, whose sheltered life has left him poorly equipped to understand and fully empathise with a worldly woman like Rachel – or indeed any woman. Bound by an outdated sense of honour and duty, his black and white vision of the world is ultimately his downfall.

Cleverly-designed sets and eerie lighting only compound the play’s suspenseful and stiflingly claustrophobic atmosphere. An absolute must-see.

My Cousin Rachel runs at the Theatre Royal Bath until Saturday November 23.