Multiverse travel is now possible, but you can only travel to worlds where your parallel self is dead. This gives people born into bad conditions where survival is unlikely a unique, if limited, value to the Elbridge Institute in walled and wealthy Wiley City.
Cara is one of those outliers, plucked from poverty and danger in the wastelands, to work as a "traverser," bringing back data from the scientists from many of the worlds where her parallel self died. She works with Dell, her Watcher, temptingly attractive yet aloof and withdrawn, a woman of old money in Wiley City.
Everything is going smoothly, and Cara has a nice apartment and a good income, and makes regular visits to her family in the wasteland settlement of Ashtown. Then another of Cara's parallel selves dies. Cara has a new world to visit, and events start to threaten Cara's dangerous secret.
It also leads to Cara discovering the dangerous secret of the seemingly kindly scientist and Elbridge CEO who invented the world-crossing technology.
