Finally, a film that asks: Why must I be a teenager in love in a country under martial law whose capital has just been nuked? From Meg Rosoff’s popular YA novel, Kevin MacDonald’s thriller stars Saoirse Ronan as Daisy, a surly American sent against her formidable will to live with cousins in some scenic but dull old English country house. It’s not all bad: The place is basically parentless, on account of mum keeping busy with death-toll forecasts for the impending third World War and related trips abroad, plus there’s a sensitive strong-silent type of about Daisy’s age (George MacKay) who’s really into falconry and allowing her to become smitten with him. That aforementioned war does become a problem, at least inasmuch as it separates Daisy from her beau, but Saoirse the survivalist, whom we may recall from Hanna, makes short work of this. Or, okay: long, kind of drawn-out work. In weird counterpoint to some cheesy cliches of teen rural-idyll romance, MacDonald stages a sufficiently harrowing odyssey for her to endure, although that too plods through its share of shopworn stuff. But the target audience probably won’t worry much about whether there’s a more effective way to split the difference between world’s-end anxiety and the possibly greater tumult of adolescent love. All the while Daisy’s head is filled with a clatter of agitated whispers, but at least — and this might be a spoiler — there’s no trauma too great to disturb her heartthrob’s cute haircut.