Female doctor Kate (Sandra Bullock) moved out of a riverside cottage in the suburbs because of her busy work. Before leaving, she put a letter in the mailbox, hoping that the next resident could help deal with the letter. Soon, she came to the old site and found a letter from architect Alex (Keanu Reeves) in the mailbox, one letter after another. It turned out that they were in different eras by two years. They were surprised and willing to become each other's pen pals. They felt each other's presence again and again in different spaces. As love grew, Alex decided to meet Kate, but they didn't know what kind of situation this love across time and space would make them experience.