Amy Reed works part-time as a PR person for a tech start-up, run by her college roommate's nineteen-year-old son, in Palo Alto, California. Donny is a baby genius, a junior at Stanford in his spare time. His play for fortune is an algorithm that may allow people access to their "multiverses" -- all the planes on which their alternative life choices can be played out simultaneously -- to see how the decisions they've made have shaped their lives. Donny wants Amy to be his guinea pig. And even as she questions his theories and motives, Amy finds herself unable to resist the lure of the road(s) not taken. Who would she be if she had made different choices, loved different people? Where would she be now? Amy's husband, Dan -- an unemployed, perhaps unemployable print journalist -- accepts a dare of his own, accompanying a seductive, award-winning photographer named Maryam on a trip to Fukushima, the Japanese city devastated by a tsunami and a nuclear disaster. Collaborating with Maryam, Dan experiences a renewed sense of excitement and possibility that he hasn't felt with his wife in a long time. But when a crisis hits at home, the extent of Dan's betrayal is exposed; and as Amy contemplates alternative lives, the couple must determine whether the distances between them in the here and now are irreconcilable.