This family adventure is set in Ember - a city on the verge of extinction. For generations the people of Ember have flourished in an underground world where the only source of light is a massive generator, but the once powerful generator is failing and the city is falling apart.

Two teenagers - Lina and Doon - race against time to unlock the secret of the city's existence - helping their fellow citizens espace before the lights go out forever.

The people of Ember believe the world outside their city is dark and uninhabitable but Lina and Doon think otherwise - their youthful hope and enthusiasm will rescue their fellow people. The film, based on Jeanne Duprau's novel, does well to convey a city heading towards destruction with images of a dimly lit sci-fi world of crumbling buildings, leaking pipes and decay.

But it falls down on its storytelling - it is never explained why the Earth became uninhabitable or why there are giant people-gobbling creatures in Ember.

It also never really delivers any exciting action sequences despite a build up of tension. Instead Lina and Doon's journey seems remarkably simple with the bad guys including Bill Murray's pot-bellied mayor never putting up any real resistence.

At the end there's a sense of disappointment at what is a very average film.