Weeks later, on a quiet dawn, Mara found a card tucked beneath her windshield wiper. The handwriting was unfamiliar: a single word—Thank you. She stared at it for a long time. The city was waking; a delivery truck rumbled by. For a moment the world felt less anonymous. It occurred to her that the act of attention could itself produce a chain; someone somewhere had seen something, and it had moved them enough to leave a small reply.