As they prepare to leave the station on “The Polar Express,” Playtone partners Tom Hanks and Gary Goetzman have made a deal for another family film with tentpole potential.

They’ve bought Jeanne DuPrau’s young adult bestseller “The City of Ember,” and are negotiating with “Edward Scissorhands” scribe Caroline Thompson to adapt it and Gil Kenan to make his live-action directing debut. Walden Media is in talks to come aboard as co-producer and financier.

In the futuristic sci-fi fantasy adventure, Earth’s citizens have moved to underground cities when the planet’s atmosphere grows too toxic. The focus is on two teens: One longs to be a messenger because the job will allow her to venture above ground, while the other dreams of working underground to repair a generator whose failure will doom the city’s power supply.

The mid-six figure, Metropolitan-brokered deal includes an option on a sequel novel DuPrau is writing. Playtone’s Diana Choi brought in the material.

Kennan, who made the live-action/animation short “The Lark,” is currently making his directorial debut on Sony’s “Monster House,” a motion capture animated film produced by Steven Spielberg and Bob Zemeckis. Zemeckis directed and produced with Playtone “Polar Express.”