She had yet to understand why their mom had left. At first she was so happy to see Nora, so happy to be back in her own body, that she hadn’t even given it a second thought. But as the initial excitement wore off, she found herself wanting to know more. She was trying to be patient. Nora’s memory had completely unspooled. It was only natural that it would take time to gather it all up. Still, her curiosity had made her restless.

She watched her mother roll up her pant legs and wade into the sea until it cut her off at the knees. Finn followed. The salt water momentarily stung the abrasions on her feet, but soon they were so cold she could barely feel them. Memories were carried to her on the wind—foghorns, seals barking, children’s delighted squeals—but she paid them no attention. She couldn’t focus on the past right now, only the present.

After they’d toweled off and put on warm socks, the Wilders sat in the open back of Zadie’s station wagon while Nora rifled through her box of cassettes. “I can’t believe you kept these,” she marveled.

“I figured you’d want them back eventually,” Zadie answered. Finn could see her sister blushing. She didn’t like anyone knowing how sentimental she actually was.

“Thank you.” Nora leaned over and gave her older child a kiss on the forehead. Zadie smiled quickly, then looked away.

Their mom closed the lid of the box and pushed it aside. Then something came over her. Hot tears sprang to her eyes. “I’m so sorry, girls. I don’t think I’ll ever forgive myself for what I did to you.”

“Will you tell us what happened?” Finn asked. She put her arm around her mother and listened with bated breath as Nora told the story of her migration.

Two thousand, two hundred, and eighty miles. That’s how far Nora had traveled. It sounded far, but it was nothing compared to the 44,000 miles Arctic terns fly from Iceland to the Antarctic and back again. Every year they circumnavigate the Earth, chasing summer to ensure that the first thing their chicks glimpse of this world is the sun.

Zadie, she explained, had been born on a brilliant spring morning. The sun was still bright the following afternoon when Nora took her daughter back to her little apartment and asked herself for the hundredth time: How did I get here? She had no memory of most of the 2,280 miles she’d traveled from Earnest to San Antonio. She had barely any memory of her hometown at all. It was as if her life had begun the moment she crossed the Texas–New Mexico border.

And when she crossed that same border eighteen years later heading in the opposite direction, her life began all over again.