The promise of seeing Scarlett Johansson fully nude is probably enough to lure lots of people into Jonathan Glazer's alien-among-us fantasy Under the Skin, and the vision doesn't disappoint. But her nakedness is the opposite of a sleazy thrill. It's so unadorned and purely human that it's entrancing on a whole other level. That Johansson's character is not human at all only adds to the pathos, and the terror, of it all. She is, as we learn early on, a killer from another world masquerading in womankind's touch-me skin. In her nakedness, she hides everything and nothing; she's treachery and softness rolled into one.
You could say the same of Under the Skin itself, a science-fiction rhapsody laced with thorns. This is the story of a girl who fell to Earth, or who was put here to do a job: drive around Scotland luring men to their doom. Most of the men are non-actors, unaware that they're being chatted up by a bona-fide movie star and captured by a hidden camera. It's an approach that invites some moral queasiness, even though all were clued in after the fact and signed release forms. But I think the way Glazer uses these performers is ultimately respectful. We're on their side -- we can't blame them for falling for this not-quite-Scarlett Johansson, because we've fallen, too.
The exact motivation of Johansson's character is never made clear, though she seems to be harvesting male flesh for either herself or her race. Really, very little in Under the Skin is clear at all. Its secrets unspool in mysterious, supple ribbons, but that's part of its allure, and its great beauty.