Scott bought an antique desk and found some letters dated from 1860's stashed in a secret compartment. The letters recorded the feelings of Elizabeth to someone she addressed as 'Dearest'. Scott felt like writing back to her, and his mother suggested him to use a stamp of that time that she has been keeping and mail it to the post office that has a hiatory dated back from 1857! Surprisingly, Scott's letter reached Elizabeth and they started a relationship that has become so mutual.
One day, Elizabeth met a Colonel and thay planned to get married when the Colonel came back from war. Scott warned her about the battle where it would claim the Colonel's life, but it was too late for Elizabeth to warn him. At the same time, the post office where Scott was sending his mails burnt down. Their last communication was from Elizabeth (who sent her letters through the secret stash), saying that Scott has returned her voice. She also sent her photograph alongside the Colonel, that revealed the resemblance of Scott. Later towards the end, Scott saw someone who looked like Elizabeth and they started a conversation. (the end)
This television movie gives me Lake House and A Message from Charity vibe.