Earth, the distant future: climate change has reduced our verdant home into a hard-scrabble wasteland. Saints and sinners, lawmakers and sheriffs, travellers and gunslingers and horse thieves abound. People are as diverse and divided as they've ever been - except in their shared suspicions when a stranger comes to town. One night a ship falls from the sky, bringing the planet's first visitor in 300 years. She's armed, she's scared - and she's looking for someone.