The Last Sensor — Joshua David Bellin

The Ecosystem will not survive.

Fifteen years ago, war nearly destroyed the City of the Queens. In the time since, Queen Rebecca's reign has been marked by reconciliation between the Ecosystem and its people. With the aid of Chief Sensor Miriam and her husband Isaac, an era of peace and prosperity seems to have been assured at last.

But then a new and unparalleled threat arises: the Ecosystem is dying, and Rebecca is powerless to restore it. Joining the Queen's guard in the search for a cure to this mysterious malady is teenage apprentice Hadassah, daughter of Miriam and Isaac. For her, the quest is deeply personal: she seeks word of her friend and guardian Sarah, the former queen of the city who has been missing for years. Hadassah's journey will take her to the ends of the earth, to a place of legendary wonder, beauty, and danger. And it will require her to tap a source of power even the queens have never imagined if she is to save her family and heal her world.

The Last Sensor is the final book in the Ecosystem Cycle, which includes Ecosystem, The Devouring Land, and House of Earth, House of Stone.