Writer/director Jonathan Glazer's art-house sci-fi allegory Under the Skin slips up on the viewer so surreptitiously that the pull of its final 30 minutes comes as a bit of a shock. The picture carries one from a state of creepy voyeuristic detachment to total immersion, and from a point of conceptual bewilderment to a place where the material's thematic threads attain sharp and radiant focus. If the film seems diffuse and aimless for its first third, we begin to realize in hindsight that such appearances are deceptive. Working from Michel Faber's 2000 novel, Glazer and scribe Walter Campbell have built the screenplay so that each scene and line of dialogue fits snugly into the broader narrative framework. Skin isn't perfect, but it is commendably ambitious and magnetic despite its flaws. In the interest of full disclosure: It is the sort of drama where one should go in knowing as little as possible; part of the pleasure comes from figuring out its secrets along the way and putting the pieces together in your mind as you go along. As there is no reasonable way to review Skin without at least discussing its setup, some spoilers may follow. The story begins in the contemporary Scottish countryside, where a motorcyclist pulls off of a highway and retrieves the corpse of an unnamed young woman (Scarlett Johansson) from a local riverbed. A subsequent scene transports us to an antiseptic white room where another female, named Laura and indistinguishable from the first (also Johansson), removes the body's clothes and puts them on; we can deduce that she has assumed this person's identity. In an extended series of follow-ups, the woman drives from one town to another in a cargo van, attempting to find young men sans family or friends, and luring them into the vehicle with her. In the first several instances of this, Glazer abruptly cuts to a later point when the passenger seat is empty once again. We naturally ask ourselves what is transpiring here and what has become of each loner. Glazer's decision to remain vague during the initial half hour suggests both a desire to toy with the audience's expectations and an attempt to foster greater investment by setting up uncertainties that deliberately keep us a little perplexed. Glazer and Campbell do ultimately show us the fates of the victims, culminating with an effects-heavy sequence so bizarre and unprecedented that it almost defies description; in the process, we can begin to deduce Laura's real nature and intentions, and by extension, those of her motorcyclist accomplice. What can be said of Laura is that, at the outset of the story, she is detached from mankind and human experience. Although, for a time, she remains icy and aloof, the circumstance of being in and around ordinary men and women gradually transforms her. In the hands of a less adroit actress, this might come off as a contrivance; with Johansson, the journey from automaton to human being really works -- she projects the character's inner metamorphosis and wholly sustains credibility. This shift comes to a head in a sequence involving a facially deformed man poised to become Laura's next victim; the encounter yields an unusual and bittersweet outcome. In the later sequences, Laura abandons her serial predation and actually attempts to enter the human race -- and is exposed to some of the finest and most ghastly behavior of our species. There is a striking, poignant contrast between the Laura we meet at the beginning, as she sits behind the wheel of the van in total control, manipulating the fates of her chosen victims with come-hither erotic pull, and the Laura we've come to know at the end -- vulnerable, lonely, quaking with fear as she encounters appalling threats to herself and her physical and emotional well-being. In that contrast resides the central irony of the film -- here is a character who apparently set out to learn about Homo sapiens in a raw but very brutal way, and by the end she has run into two extremes that between them seem to illuminate the whole spectrum of the human experience. That fascinating concept -- and the empathy that we eventually begin to feel for the protagonist -- gives the movie stunning resources that it doesn't initially seem to possess. Much less satisfying is the extent of Glazer's narrative opacity. Though in many scenes the movie's enigmatic quality feels suitably intoxicating, there are a couple of specific occasions in which the obscurity of the story is close to unbearable. For example: In principle, Laura should indeed turn a corner when confronted with the deformed man, and her subsequent arc makes sense, but the characters' shared scene in her lair feels infuriatingly oblique, populated with a couple of arcane lines of dialogue and a dizzying flash of special effects. Her change of heart and his response need to be more clear-cut and well-defined to really deliver. Also: Laura's interactions with Andrew (Paul Brannigan), a kindly man she meets in the second half of the picture who briefly takes her into his home, need to be more transparent than they are. Again, we can see what Glazer is going for on a conceptual level -- attempting to depict the pinnacle of earthly bliss with a romantic substory -- but Andrew is such an enigma and we see so little actual communication between him and Laura that these occurrences don't achieve the degree of emotional pull that they would in more conventional directorial hands. Those setbacks aside, though, this is still a marvelous movie. Per Glazer's prior features -- Sexy Beast (2000) and Birth (2004) -- Skin exists on a much higher plane than most current mainstream features and should be embraced as such, even though it will almost certainly confound less adventurous filmgoers. It's an elegantly conceived and executed motion picture, given lift by a brilliant, courageous central performance, a breathtaking visual schema courtesy of cinematographer Daniel Landin, and deep, multilayered philosophical underpinnings.