Lin Ye is a postman who travels through the cracks in time. His mission is to deliver letters that have been forgotten by time - some are from Shanghai alleys in 1920, and some are sent to the Mars base in 2077.
Once, he picked up an unsigned letter from a crack. The writing on the letter paper was blurred by time, but the words "Waiting for my return" can be seen. Following the clues in the letter, he found the soldier who wrote the letter on the battlefield in 1945, and the old man who received the letter in a nursing home in 2023. When the old man received the letter tremblingly, Lin Ye discovered that he was not only a postman, but also a stitcher of time, using a letter to reconnect the broken thoughts.
