Handsome and richly atmospheric, writer-director Roger Michell’s adaptation is subdued grown-up fare that doesn't quite sustain the “did she or didn't she” mystery for its entire running time. But there's enough dark sizzle between leads Rachel Weisz and Sam Claflin to keep the audience involved through the underpowered middle stretches before the film regains its footing, delivering a disquieting shiver of a conclusion.
The late-1830s action unfolds almost entirely on an estate near England's southern coast, where Philip Ashley (Claflin) prepares for the arrival from Florence of Rachel (Weisz), the widow of his beloved cousin and guardian Ambrose and, he's certain, Ambrose’s killer. As Michell establishes with tantalizing concision in the pre-title sequence, Ambrose’s letters home had taken a couple of drastic turns in recent months, from enchantment to mistrust to outright terror. The new wife he initially describes as “my kindest companion” soon becomes “my torment”, and before Philip can respond to the desperate plea his cousin has hidden in cramped scribble on the inner flap of an envelope, Ambrose is dead from a brain tumour.
Fired up for retaliation, Philip is instead instantly disarmed by the Italo-English beauty in widow's garb. With her cosmopolitan elegance, she's clearly the more self-possessed of the two. But even so, the younger man's resemblance to her husband unnerves Rachel.
In a household where the only females are of the canine persuasion, Rachel soon becomes de facto hostess, charming even the crotchety old servant Seecombe (a scene-stealing Tim Barlow), who had dreaded her arrival. Philip, in turn, morphs from sworn avenger to foolhardy protector, believing it his duty to right the matter of Ambrose’s unfinished will and ensure that Rachel will have a proper inheritance.
In individual scenes, though, the questions that fuel the story continue to burn even when the narrative transitions are less than smooth. Those questions course beneath the Victorian etiquette like a fever: Is Rachel a scheming, murderous fortune hunter or a woman demonised for her modernity?
Had Ambrose perceived her true intentions, or was he deranged from his illness?
There's a timeless psychological power to du Maurier’s story. Though it specifically addresses 19th century codes governing marriage and property, its concerns with morality, social expectations and female independence still resonate. But above all, My Cousin Rachel is a beautifully tangled web of good and evil, innocence and experience. - The Hollywood Reporter