Hall wants the play to remain true to the original story but has emphasised the enormity of the task facing Rachel and Theo.
She can't wait to hear ideas about how the action scenes should look and with seasoned theatre and opera director Sara Brodie at the helm, actors are in the first throes of making the story come alive.
They'll show how far they've come at ATC's annual festival of new work, The Next Stage, in semi-staged performances later this month.
The performances are open to the public, who are asked for feedback at the end of each one so the playwright and production team can develop scripts.
Campbell says she hopes families will come along to see Under the Mountain which, when it's completed, could run at ATC's new Waterfront Theatre due to open late next year. It is one of three scripts-in-development at this year's Next Stage.
First up is Peer Gynt Recycled, a response to playwright Henrik Ibsen's 1876 Peer Gynt by ATC's inaugural Patrons Playwright Fellow Eli Kent. Kent has had a busy year travelling to New York to stage All Your Wants and Needs Fulfilled Forever while another of his collaborative works, Like There's No Tomorrow, played at the Wanaka Festival of Colour.
Anahera is the third work in development at this year's Next Stage. Written by Emma Kinane, it focuses on a young Maori social worker who suspects a middle-class pakeha family of child abuse.
Performance
What: The Next Stage
Where and when: Auckland Theatre Company, 487 Dominion Rd, Balmoral, November 13-15; see atc.co.nz