Because it serves up Armageddon with a side order of teen romance, How I Live Now is not always credible. But as a portrait of a surly 16-year-old whose internal crisis is overtaken by an external one, the movie is persuasive.
For that, credit goes partly to director Kevin Macdonald, but mostly to his star, Saoirse Ronan. Playing a neurotic urbanite who learns to survive in a war-ravaged landscape, the actress is, appropriately enough, a force of nature.
The opening sequence, set in an unidentified British airport, announces that the movie shares its lead character’s perspective. We’re practically inside the head of Ronan’s Daisy, and it’s a noisy place. Her thoughts — angry, insecure, self-rebuking — compete with the glam-rock song pulsing from her purple headphones.
The film’s script was adapted from Meg Rosoff’s 2004 novel, some of whose fans are unhappy with the alterations. In the book, Daisy is anorexic; in the movie, she’s obsessive-compulsive, with a fear of germs and gluten and a hand-washing fixation. Also, the cousins she’s about to meet have been condensed; one onscreen boy combines the roles of two in the original tale.
Daisy was raised in New York by her American father; the dead mother she doesn’t remember was the sister of Aunt Penn (Anna Chancellor). Penn’s children are teenagers Edmond (George MacKay) and Isaac (Tom Holland) and their little sister, Piper (Harley Bird). While the two younger kids are chatty, Edmond is a handsome brooder.