Family/Drama. Saoirse Ronan, Harry Treadaway, Bill Murray, Toby Jones, Tim Robbins, Mackenzie Crook, Martin Landau, Marianne Jean-Baptiste, Liz Smith, Amy & Catherine Quinn. Director: Gil Kenan.

During the ’50s and ’60s, the spectre of nuclear war loomed large. Nations were crippled with fear and paranoia, constructing nuclear fallout shelters to sustain the population for months, if not years after an attack.

Jeanne DuPrau expanded the idea of subterranean refuges in her first novel, The City Of Ember, which was published in 2003.

In this first book of an ongoing series, she imagined an entire underground community powered by a massive generator, cocooned from the apocalyptic horrors on the surface. The human race endures while the planet heals.

Director Gil Kenan accepts the unenviable task of bringing DuPrau’s vision to life to realise an entire city of ramshackle homes and business, laid out in concentric circles, with a town square at the centre.

These three-storey sets, created in a hangar at Belfast docks, are spectacular — shabby and bathed in light from hundreds of bulbs.

For the past 200 years, the bustling metropolis of Ember has survived thanks to a generator, but food supplies are dwindling and machinery is about to fail.

Graduate student Doon Harrow (Treadaway), who toils in the pipeworks under narcoleptic mentor Sul (Landau), tells his inventor father (Robbins), “I’m getting into that generator, whatever it takes.”

Feisty classmate Lina Mayfleet (Ronan) feels just the same. Lina stumbles upon the answer when she discovers a metal box containing cryptic instructions.

City Of Ember feels a tad sluggish even at 94 minutes, with just two action set pieces (a close encounter with a giant tentacle-nosed rat at the midway point and a high speed, log flume finale).

Digital effects are used sparingly, but are noticeable by their clumsiness against such impressive production design.

Ronan and Treadaway are both endearing but we don’t spend enough time with either of their adventurous urchins to feel we know them before the grand adventure begins in earnest.

Murray plays his corrupt official so low key, he’s almost lifeless. Landau, Robbins and Jean-Baptiste are all much better than their meagre supporting roles merit.