Bill Murray, Saoirse Ronan and Toby Jones have signed onboard Walden Media & Playtone's "City of Ember," a fantasy feature based on Jeanne DuPrau's book.

Murray will play the larger-than-life mayor of Ember, an insular world lit only by a magnificent number of glittering street lights. However, the once-powerful generator is failing and the lamps are flickering.

Two teenagers (Ronan plays one) must search the city for clues that will unlock the ancient mystery of the its existence and help the citizens escape before the lights go out forever. Jones will portray Barton Snode, the mayor's right-hand man.

Gil Kenan ("Monster House") directs, Caroline Thompson adapted the screenplay, and shooting begins this Summer in Belfast. 20th Century Fox will release the film next October.