The poster for moody thriller How I Live Now shows Atonement actress Saoirse Ronan staring sullenly into the distance, headphones firmly blocking out the world around her.

You might assume from this striking image that Kevin Macdonald's film follows a familiar route as the one signposted 'Awkward Teen Who Finds Out That Life Isn't That Bad After All'.

Thankfully, the picture treads a different path.

Adapted from Meg Rosoff's young adult novel of the same name, the story centres on a New Yorker called Daisy (Ronan), who suffers from obsessive tendencies and is sent to England to spend the summer with her British cousins in the country.

Initially, there is friction as 15-year-old Daisy meets her Aunt (Anna Chancellor) and cousins, sensitive Edmond (George MacKay), sweet natured Isaac (Tom Holland) and bubbly baby of the bunch, Piper (Harley Bird).

No sooner has Daisy settled in to her unfamiliar surroundings than things start to get really weird.

After her aunt goes to Switzerland for business, Daisy and Edmond start to fall in love.

The young lovebirds have to put their romance on hold when a series of bombs hits the UK, all electricity is cut off and war is declared.

When boys and girls are separated, a distraught Daisy and Piper are packed off to live with a peculiar older couple in a Barratt Home in the middle of nowhere.

With Edmond's parting message to find a way back home ringing in Daisy's ears, she and Piper escape from the house and try to track down Edmond and Isaac.

Life in the wilderness becomes dangerous and before long, Daisy and Piper's lives are in peril and depressingly enough, they're no closer to the boys.

Guided by Edmond's words and vivid dreams of him, Daisy ploughs on and tries to reunite with her beloved.

Acclaimed director Macdonald recently said that audiences might be divided into those who prefer the first half and those who favour the second.

While there may be people who enjoy the slightly softer opening act, there is a consistently dark thread throughout the film that means the second half doesn't feel out of place.

The film is blessed with rock solid performances from the young cast and the glorious Welsh countryside.

A pleasantly dark antidote to the usual sugary doses of big screen teen angst.