We’d purchased two small travel bags and some clothes and toiletries in Monterrey to give ourselves the appearance of proper travelers. We’d also been told—at least three times—to pick up breathers. According to the sales clerk who sold Rafael his shaving kit, they were a necessity of life in Tenochtitlán. She’d barely suppressed a bemused smile when I said we’d already bought two top-of-the-line Fellini-Med models, noted for their effectiveness against both particulates and noxious gases. Only when we reached the capital did I find out why that was so funny.