Mara found the key in the pocket of her grandmother's winter coat, an old brass thing worn smooth by years of handling. Her grandmother had died in the spring, and nothing in the house seemed to fit the key. All the same, Mara could not bring herself to throw it away.
That evening she took the last ferry across the bay. She was turning the key over in her fingers, watching the lights of the harbor slip by, when she noticed that the old man sitting opposite her was doing exactly the same. His key was identical to hers. "Where did you get that?" he asked quietly. "From my grandmother's coat," said Mara. The old man lowered his eyes and smiled. "Then you must be her granddaughter. My name is Aldo. Your grandmother and I were best friends when we were children. Sixty years ago we locked a wooden box under the old pier, and we promised to open it when we were both old."
The next morning, at low tide, they walked out together over the wet sand and found the box. Inside were two small paper boats and a note: "We'll sail again." Aldo laughed and cried at the same time. Mara tore a page from her notebook, folded a new boat, and they sailed it together.