When Jonah met eight-year-old Mira, he wasn’t looking to become a father. He was cleaning up the sticky fingerprints on a cardboard box in the apartment he’d just agreed to sublet when an intercom buzzed and the woman downstairs—Mira’s mother—asked if he’d mind checking the mail. One errand turned into moving boxes, which turned into weekend dinners, which turned into a neighbor who learned Mira’s favorite color, the rules of her favorite video game, and how to make breakfast pancakes just the way she liked them: a tiny tower with a smiley face of syrup.