From the earliest scenes, when American teenager Daisy (Saoirse Ronan) arrives to stay with her British relatives deep in the countryside, How I Live Now has a disorienting and eerie quality.
The landscapes are beautiful but the impressionistic camerawork and editing induce a sense of foreboding. Daisy is fascinated by her silent, handsome young cousin Eddie (the ubiquitous George MacKay) but, just when the film seems to be turning into a rites- of-passage drama about first love, there is a rumbling on the soundtrack and snow begins to fall.
There has just been a nuclear attack on London and we are cast into the world of dystopian sci-fi. Adapted from Meg Rosoff's novel, How I Live Now carries echoes of everything from Lord of the Flies to Quatermass IV.
It is beautifully directed by Macdonald, who combines flights of lyricism with scenes of utter brutality. There is also a very steely performance from Ronan as the young heroine fighting for survival.