BEFORE I GO TO SLEEP: CHI E' COLUI CHE DORME NEL LETTO DELLA SMEMORATA CHRISTINE (NICOLE KIDMAN) SE NON SUO MARITO?! DALL'ELETTRIZZANTE ROMANZO DI S. J. WATSON ALLA CELLULOIDE DI ROWAN JOFFE

NICOLE KIDMAN AND COLIN FIRTH PLAY SUB-HITCHCOCKIAN GAMES IN THIS DIVERTING BUT DOPEY ADAPTATION OF S.J. WATSON'S BESTSELLER.

“Before I Go To Sleep” is a risky title for a genre exercise intended to keep viewers bolt upright in their seats, handing mirthful critics a ready-made punchline at the first sign of lethargy. The good news is that Rowan Joffe’s adaptation of S.J. Watson’s 2011 publishing phenom is far from a snooze; the bad news is that it’s the film’s escalating, po-faced ludicrousness that holds our attention. Starring a typically hard-working Nicole Kidman as a short-term amnesiac unsure whether she’s being played by her husband, her shrink or both, the film’s wildly contrived premise could be more pithily described as “Alfred Hitchcock Presents: 50 First Dates.” With David Fincher’s similarly targeted “Gone Girl” already siphoning its buzz, this dopey diversion will need the novel’s fans to turn out en masse to

avoid being forgotten by morning.

A planned Halloween release Stateside — weeks after the film’s Sept. 5 release in Blighty and elsewhere — might lead auds to expect an out-and-out frightfest, but for the bulk of its running time, “Before I Go To Sleep” is more of a psychological puzzle picture, reserving the would-be white-knuckle stuff for its final few reels. If it still fails to stir up too many screams, that could be because the narrative’s complex network of holes is so apparent by that point that any real sense of peril is hard to sustain — despite the quivery efforts of Kidman, an actress who has long done hunted fragility better than just about anyone in the business. Having already impersonated Grace Kelly in one bad film this year, she has a second bite at the cherry here: Her vulnerable, terminally addled but resourceful heroine Christine Lucas is essentially

a terrorized Hitchcock blonde in more sensible shoes.

There’s a Cary Grant substitute, too, in Colin Firth’s stiffly affectionate, not entirely forthcoming husband figure Ben, on whose dulcet tones it falls to provide much of the initial exposition. Christine, it turns out, has suffered from anterograde amnesia — that condition, long beloved of screenwriters, that prevents the formation of new memories — ever since nearly losing her life in a horrific attack several years prior. Every day, she wakes to become freshly acquainted with Ben and the moneyed, minimalist house they share in outer suburban London; whatever new information she gleans during the day is wiped clean by morning, as her memory resets to a 20-year-old state.

What Ben doesn’t know, however, is that Christine has been keeping a video diary at the behest of her psychologist, Dr. Nash (Mark Strong), a device that allows her some semblance of cumulative memory —

a higher-tech equivalent of the similarly debilitated Guy Pearce’s Polaroid-and-tattoo method in “Memento.” “Sleep” opens with her recording a particularly panicked bedtime entry before skipping back, as is de rigueur in mainstream thrillers these days, to the recent past. Nash calls Christine on a daily basis to reintroduce himself and remind her of the diary’s existence. In this way, she pieces together fragments of her personal history that Ben, supposedly out of concern for her mental well-being, has kept from her — notably her estranged best friend, Claire (Anne-Marie Duff), and, crucially, her departed son Adam, whom Ben claims was lost to leukemia some time after her accident.

With the help of this expanding aide-memoire, Christine inches toward the root of her trauma; furthermore, at a sort of one-step-forward-two-steps-back pace, she begins to realize that her domestic life is not what it appears to be. To unpick the numerous lapses in

logic and credibility that keep this plot suspended — most of them, to be fair, inherited from the source novel, from which Joffe’s screenplay makes few drastic deviations — would be to enter severe spoiler territory. It is fair, however, to note that the film never answers the question of how Nash, without the knowledge or consent of the keenly protective Ben, came to treat Christine in the first place.

That’s a gap from which a torrent of other head-scratching uncertainties spill, while the unorthodox nature of their therapy sessions keep in play the possibility that Nash, rather than Ben, might be the one concealing critical secrets from our heroine. (Why do they keep rendezvousing in desolate parking lots, if not simply to honor sacred thriller tradition?) The film’s interest in, or understanding of, Christine’s fascinating condition is limited even by the superficial standards of mainstream movie psychology: Beyond the pinched,

nervy undertow of psychic pain in Kidman’s performance, it’s treated as little more than a convenient quirk to get the film’s motor running. Nash, for his part, tosses around elementary terms like “transference” with scholarly gravitas. Between her husband and her doctor, Christine has to deal with so much measured mansplaining on a daily basis, it’s a wonder she doesn’t use her camcorder to bat both of them around the skull.

Wittier filmmakers have managed to sell audiences on even sillier plots than this one, but Joffe, a proficient stylist who previously flailed with a loftier literary source in 2010’s disastrous “Brighton Rock” update, takes the material entirely at face value — and a stonily serious face it is, too. There’s perilously little playfulness to be found either in the script or its otherwise handsomely ashen cinematic treatment; even Melanie Ann Oliver’s efficient but staid editing makes little attempt to put

viewers in the protagonist’s mind or creatively mirror her cyclical confusion. Top marks among the below-the-line team go to production designer Kave Quinn, whose chic but alienating appointment of Christine’s surroundings (all slate-hued walls and skeletal Scandinavian furniture) convincingly creates the sense of a home that, both physically and psychologically, has never quite been her own.

Performance-wise, the film is constructed as “The Kidman Show,” though the star’s deliberate turn isn’t always in sync with the more histrionic demands of the filmmaking or Edward Shearmur’s jumpy score. Strong offers a warmly neutral bedside manner, while Firth seems detached beyond the remit of his inscrutable role. With “Sleep” coming mere months after his and Kidman’s more attentive collaboration in “The Railway Man,” in which Firth’s character was the one with psychological demons to exorcise, these well-matched co-stars have surely earned the right to have a little more fun together — or, failing

that, at least a good restorative nap.