My sister's arrival in Rome a few days later helped nudge my attention away from lingering sadness over David and bring me back up to speed. My sister does everything fast, and energy twists up around her in miniature cyclones. She's three years older than me and three inches taller than me. She's an athlete and a scholar and a mother and a writer. The whole time she was in Rome, she was training for a marathon, which means she would wake up at dawn and run eighteen miles in the time it generally takes me to read one article in the newspaper and drink two cappuccinos. She actually looks like a deer when she runs. When she was pregnant with her first child, she swam across an entire lake one night in the dark. I wouldn't join her, and I wasn't even pregnant. I was too scared. But my sister doesn't really get scared. When she was pregnant with her second child, a midwife asked if Catherine had any unspoken fears about anything that could go wrong with the baby—such as genetic defects or complications during the birth. My sister said, "My only fear is that he might grow up to become a Republican."

That's my sister's name—Catherine. She's my one and only sibling. When we were growing up in rural Connecticut, it was just the two of us, living in a farmhouse with our parents. No other kids nearby. She was mighty and domineering, the commander of my whole life. I lived in awe and fear of her; nobody else's opinion mattered but hers. I cheated at card games with her in order to lose, so she wouldn't get mad at me. We were not always friends. She was annoyed by me, and I was scared of her, I believe, until I was twenty-eight years old and got tired of it. That was the year I finally stood up to her, and her reaction was something along the lines of, "What took you so long?"

We were just beginning to hammer out the new terms of our relationship when my marriage went into a skid. It would have been so easy for Catherine to have gained victory from my defeat. I'd always been the loved and lucky one, the favorite of both family and destiny. The world had always been a more comfortable and welcoming place for me than it was for my sister, who pressed so sharply against life and who was hurt by it fairly hard sometimes in return. It would have been so easy for Catherine to have responded to my divorce and depression with a: "Ha! Look at Little Mary Sunshine now!" Instead, she held me up like a champion. She answered the phone in the middle of the night whenever I was in distress and made comforting noises. And she came along with me when I went searching for answers as to why I was so sad. For the longest time, my therapy was almost vicariously shared by her. I'd call her after every session with a debriefing of everything I'd realized in my therapist's office, and she'd put down whatever she was doing and say, "Ah . . . that explains a lot." Explains a lot about both of us, that is.

Now we speak to each other on the phone almost every day—or at least we did, before I moved to Rome. Before either of us gets on an airplane now, the one always calls the other and says, "I know this is morbid, but I just wanted to tell you that I love you. You know . . . just in case . . ." And the other one always says, "I know . . . just in case."

She arrives in Rome prepared, as ever. She brings five guidebooks, all of which she has read already, and she has the city pre-mapped in her head. She was completely oriented before she even left Philadelphia. And this is a classic example of the differences between us. I am the one who spent my first weeks in Rome wandering about, 90 percent lost and 100 percent happy, seeing everything around me as an unexplainable beautiful mystery. But this is how the world kind of always looks to me. To my sister's eyes, there is nothing which cannot be explained if one has access to a proper reference library. This is a woman who keeps The Columbia Encyclopedia in her kitchen next to the cookbooks—and reads it, for pleasure.