At the frontier post office five thousand meters above sea level, postman Jiang Ye always received a blue envelope without an address on a snowstorm night. Until one day, Lin Che, a meteorologist who came to teach at the observatory, discovered that the postmark dates on the letters were ten years ago - and the name of the sender "Alai" was engraved on the stone tablet of the old weather station buried by an avalanche. When Jiang Ye used his body temperature to melt the frozen letterhead, the snow particles in the letter suddenly gathered into the contour map Alai had drawn before his death. Lin Che's anemometer detected a voiceprint frequency that did not belong to this world late at night: "I am waiting at the snow line for you to send the clouds into a letter." The two followed the clues in the letter and broke into the observatory sealed by ice crystals. They found that in the weather log left by Alai, the trajectory of each cloud was marked with an arrow pointing to Jiang Ye's childhood. And when Lin Che used laser radar to penetrate the snow layer, the boy lying in the ice coffin ten meters underground actually had the same birthmark as Jiang Ye - it turned out that in the avalanche ten years ago, someone used his life to weave a snowfall that spanned time and space for his lover, and all the unsent love letters were long-lasting love written and melted by snow particles in the clouds.
