At the end of the twenty-first century, Earth is under the control of a single intelligence, the apparently benign One True. Mars, meanwhile, is slowly terraforming, and the human settlers there are still free of One True's control...but you still need a pressure suit to survive outside, and it will be a century or more before the planet's fit for terrestrial life.

Terpsichore Murray is growing up on Mars. She wants to quit school and become, like her father, an ecoprospector. He has other ideas; not only does he want her to stay in school, he wants her along on his next long trip, conducting a group of younger kids from the highlands at Mars' equator back to school in Wells City.

What happens next will change Terpsichore, will change Mars, and will open the door to a new chapter in the history of intelligent beings in the solar system...all of them.