Near the melting edge of Calder Glacier, a research station doubles as a post office for letters frozen decades ago. As ice calves, envelopes surface, sealed and stamped from eras when handwriting mattered. Dr. Elsie Tran catalogs each letter and attempts delivery. Some addresses no longer exist. Others lead to descendants. One day, a packet emerges sealed in wax, addressed simply to "Future." Inside are letters from a 1912 expedition team, optimism crisp as cold air. They write about a new world made better by exploration. Elsie delivers one to a museum, another to a school. Children read about ice that seemed endless. They ask why it is smaller now. Elsie cannot soften the answer.
More letters appear, some mundaneāgrocery lists, love notesāothers prophetic. A man warns of industry's smoke; a woman writes about a dream where glaciers weep. The post office becomes pilgrimage for people wanting to write back. Elsie sets up a reverse mailbox: letters to the past, never to be read by their intended. Still, people write apologies, thanks, reassurances. The glacier groans. One afternoon, a fresh letter slides out, ink unbled, addressed to Elsie by name. She has told no one to expect her. The letter contains coordinates and a single line: "You will find our footprints with yours." Elsie hikes to the spot and finds an old boot print melting next to her own. She presses her hand into the slush, bridging a century with a palm. The post office keeps delivering until the glacier is gone. The last letter is blank except for a watermark shaped like ice, as if the glacier signed its own farewell.
After the ice retreats, the station becomes a museum. Tourists mail letters to "Future Earth" out of habit. Elsie retires, but she keeps the reverse mailbox on her porch. Neighbors drop in notes addressed to great-great-grandchildren. Elsie writes one final letter to the glacier itself: "Thank you for the mail. I am sorry we did not protect your address." She slides it into the empty slot. The wind delivers it somewhere only meltwater can read.