I first saw Karolina outside the Sumesa on the corner of Avenidas Oaxaca and Álvaro Obregón. She was smoking a stubby cigarette, a sled-like backpack hitched to her shoulders. I stopped short, felt my heart lurch. Could it be? Karolina was my brother’s ex-wife; they’d divorced five years ago, in Seattle, and I’d not seen her since. Right before their divorce, she had gone missing for fifteen days, an event still marked by dread and shame. The second time I saw her was by the bus stop on Avenida Michoacán. The third sighting was in Parque México, late at night. I had decided to walk back from a work dinner in Roma Sur to the hotel because I was having trouble sleeping and a long walk before bed—tracing the park’s serpentine paths, imagining the alertness being drained from my body one step at a time—seemed like a preemptive strike against insomnia. The dog run was empty except for a young man throwing a tennis ball for a German shepherd. The owner was wearing sunglasses, despite the hour. I was just past the run, in the thick green center of the park, when I came upon Karolina asleep on a bench, squeezing her giant backpack like a lover.