The Only Living Girl 2

When members of her city are poisoned by an unknown element, Zandra Parfitt, known as “Zee,” discovers there's only one place to find help: Dianoia, the deadly catacombs under an invisible city. But when Zee, and her friends, embark on their quest, they quickly realize that their lives are also at risk. And if their adventure doesn’t destroy them… the Consortium and the diabolical Doctor Twice are lurking in the wings to finish the job.