Mack has moved so much in his life that every phone number he comes across seems to him to be one he’s had before. I swear this used to be my number,” he says, putting the car into park and pointing at the guide book. 923-7368. The built-in cadence of a phone number always hits him the same personal way: like something familiar but lost, something momentous yet insignificant—like an act of love with a girl he used to date.

“Just call,” says Quilty. They are off Route 55, at the first McDonald’s outside of Chicago. They are on…