“That's one of our speculations, by the way. That the prior version of history that this one overwrote was horrible. Complete geopolitical mayhem; half of New York City is underwater. The United States is headed toward civil war, or ruled by an artificial-intelligence construct, or some such other thing. Real end-of-days stuff. That the instances of ourselves who existed in that history figured out what we have: that the invention of the causality violation device was the cause. That in that prior version of history, Rebecca did not die in a car accident. That she went back to the past on a mission, as a volunteer, well aware of her sacrifice.”