Two very different approaches to science fiction are on offer this week.

In The Zero Theorem, we have Terry Gilliam's "everything but the kitchen sink" overload of ideas and production design. And then there is Jonathan Glazer's Under The Skin, one of the most abstract, minimalist films you will see this or any year. The first left me cold, the second riveted.

Under The Skin is based on the novel by Michel Faber, which concerns an alien on earth - in Scotland, to be precise - who adopts the form of a woman while seducing and abducting men, for nefarious purposes. While the novel elaborates the alien's motives and the fate of the men, Glazer pares everything to the bone - there is no explication at all, and very little dialogue. The result is strange and unsettling.

The opening sequence establishes Glazer's lo-tech method. A growing light, discs moving towards each other, a disconnected voice, an eye - these images and sounds combining to suggest the transformation of the alien into its human form, which happens to be that of Scarlett Johansson.

A dead woman's body is delivered by a motorcyclist, who will appear throughout the film, a sort of handler for this extra-terrestrial operative. In a white space as pronounced as the black one that will eventually engulf her victims, the naked Johannson undresses the woman and puts on her clothes. The precise sound design of the film is never more evident than here, as the brusque removal of the clothes, the sound of textile leaving flesh, rams home the clinical procedure of the alien's identity theft. Then it's to the shopping mall for some slightly less trashy clothes and lipstick, before hitting the road in her white van, driving around Glasgow and its environs, on the prowl.

If the Glasgow scenes seem authentic, it is because to some extent they are. Almost unrecognisable in a black wig and with a received Pronunciation Accent, Johansson was in character as she interacted with real people, hidden cameras recording the action. If a man and his responses had potential, he was told what was happening and asked if he wanted to take part.

It is worth being aware of the process, for its rewards are conspicuous. As Johansson walks around the city, drives through a Celtic crowd and is cajoled into entering a nightclub by a group of young ravers, we get a fulsome sense of human life, as coolly observed by someone who has never seen it before. Young and old, wealthy and poor, healthy and infirm, faces we take for granted in the day-to-day are lent a touching immediacy by this alien gaze.

Johansson is not only commendably game in these scenes, but perfectly pitches her character as both wide-eyed outsider and predator. This harmless-looking, comely young woman is deadly, the extraordinary way in which Glazer visualises her victims' fate at once aesthetically pleasing and terrifying.

When an encounter with a deformed man seems to throw the alien out of balance, she leaves the city for the west coast. Here she enjoys some surprising domesticity (a moment in which the Hollywood actress watches Tommy Cooper on the television is priceless), before finding that humans, themselves, can be predatory.

While Glazer's debut, the gangster movie Sexy Beast, showed a great stylist at work, it was Birth (in which Nicole Kidman believes her dead husband has been reincarnated as a boy) that revealed his penchant for the outlandish. Under The Skin's mode of storytelling will not be to everyone's taste, but succumbing to its strangeness is to experience an atmospheric, disturbing, thought-provoking mood piece that crawls under your skin and stays there.