Miss the opening scene of Gil Kenan’s tween-aimed fantasy and you’re in for a baffling time. With the world as we know it about to end, an underground refuge has been built to keep humanity safe for 200 years…

… after which the generator is about to pack up, everyone’s hungry and, unless someone fixes the boiler or finds a way out, it’ll be Doomsday all over again.

Doon Harrow (Treadaway, Control) is determined to stop the rot. But come Assignment Day when youngsters discover their place in the workforce, Doon is made a messenger while Lina Mayfleet (Ronan) must enter the Pipeworks.

So they swap jobs. Independently, they learn of a secret escape route from the city and that fat-cat Mayor Cole (Murray) is up to no good.

It also becomes apparent that Doon’s inventor dad (Robbins) knows more than he’s letting on and that there’s more to narcoleptic old plumber Sul (Martin Landau) than meets the eye.

The city’s salvation is literally in their hands: in the form of a mysterious metal box which Lina’s granny (Liz Smith) had forgotten about.

As they’re figuring things out, the intrepid pair move to expose Cole, avoid other Machiavellian miscreants like limping storeman Looper (Crook), and somehow keep Lina’s little sister out of harm’s way.

While creating his dystopian underworld, director Kenan was clearly under the influence of filmmakers Terry Gilliam, Jeunet and Caro (particularly The City of Lost Children) and animation maestro Hiyao Miyazaki.

Similarly, several collaborations with Tim Burton suggest that Caroline Thompson (Edward Scissorhands, Corpse Bride) was just the screenwriter to bring the wondrous best out of Jeanne DuPrau’s first ‘Ember’ novel.

And with a cast including Toby Jones as Cole’s lackey, two Oscar winners (Robbins and Landau), three nominees (Murray, Ronan and Marianne Jean-Baptiste) and the redoubtable Smith, City of Ember had all the parts to add up to something fantastic.

But while the production design and pacing are to be admired, the chase throws up nothing new, save for a room full of loom threads and giant, man-eating mole - which somehow got in without anybody noticing.

Since we’re nit-picking, why did the city’s builders make the escape instructions so complicated to begin with?

Some of the performances are questionable too. Ronan continues to build on the promise of Atonement but Treadaway’s Doon is a po-faced yawn, and rarely has a pantomime villain looked as disinterested as Murray’s mayor.

After the Oscar-nominated wizardry of Monster House, Kenan also underwhelms with an unconvincingly X-boxy finale.

Passable family fare, but Ember too often smoulders when it needs to fire.

Elliott Noble