There is something very levelling about seeing a major Hollywood star walking past Primark. And not just any Hollywood star but Scarlett Johansson, twice crowned Esquire’s “Sєxiest Woman Alive”, three times Woody Allen muse, Bafta winner, noted beauty. Yet, there she is, in her latest film, in a pair of stonewashed jeans and a fake fur coat, walking down a busy shopping street in Glasgow and, well, blending in. She looks normal. Ordinary, even. Strip a star of their Hollywood get-up, remove them from their Bel Air mansions, and it turns out that they look just like the rest of us.

Only Johansson is different. Theoretically, this is because, in Under the Skin, a low-budget sci-fi indie adapted from a Michel Faber novel, we know she’s an alien. In reality, it’s because we know she’s Scarlett Johansson. We watch her prowling the outskirts of Glasgow, the in-between lands of industrial parks and council estates, looking for fresh man meat, and there is an eerie sense of alien universes colliding. Scenes include Scarlett Johansson on a bus. Scarlett Johansson being given directions to Asda. And Scarlett Johansson sitting in front of an electric fire in a council house watching Tommy Cooper on TV.

It turns out that transplanting a major Hollywood celebrity to a down-at-heel, working-class Scotland is about as close as you can get to seeing an alien walk among us. Celebrities may not be an actual master race – yet – but there is something weirdly jarring about seeing someone familiar from a thousand red-carpet pH๏τographs, walking down an ordinary high street full of the ordinary faces of ordinary lives.

When I meet her, however, Johansson, 29, is back in full Hollywood mode. She’s been installed in a fancy suite in New York’s Waldorf Astoria and has shed the ugly jeans and cheap boots. She’s in spiky heels and a silky top and is groomed and coiffed with eyelashes like a camel’s and a river of shining blond hair that flows around her shoulders. She is surrounded by a small army of publicists and minders. She looks neither ordinary nor normal. (Nor, noticeably, pregnant, as various newspapers claimed last week.)

I’ve just seen her in action at a press conference where she’d gone off on a long riff about Jonathan Glazer, the British director of the film who she calls a “visionary” and a “genius”. And when I meet her, she says what an easy and enjoyable film it is to talk about. “Because it brings up so many questions. One of the journalists that I was talking to today, we ended up talking about the relativity of time. Whereas, normally, it’s like ‘So, what do you find Sєxy in a guy?’ Or, ‘If you had a superpower, what would it be?’”