I haven't seen the new movie "The Lake House," which concerns an exchange of letters between a man and a woman living in the same location but separated by time. Dan Curtis was intrigued by this theme as he talked about it in connection with his Hallmark television production "The Love Letter." The same general idea had been used earlier on DS, though not as a love story. I'm forgetting the details, but Barnabas and Julia were living in different times and Barnabas needed to get back to his own time. I believe he wrote a letter which was placed in the secret compartment of a desk at the Old House, and later found by Amy during the present day. As I think of it, one could say that the letter exchanged between Barnabas and Julia across the centuries was emblematic of the care they felt for one another. The plot of "The Love Letter" has been described as : "Soulmates exchange letters across time through an antique desk
Mr. Curtis' production of "The Love Letter" clearly acknowledged its source, a short story titled "The Love Letter" by Jack Finney.
The theme of a love story across time probably is most widely known from the movie "Somewhere In Time," based on a Richard Matheson novel, which seems to have been inspired by various stories by Jack Finney. A line in the movie refers to a fictional physicist named "Jack Finney," hence Mr. Matheson's homage to Finney.
The screenplay for "The Lake House" was written by a Pulitzer Prize-winning and Tony Award-winning dramatist, so it ought to be of high quality. Credits for the movie do not acknowledge Finney as the source for the central idea of an exchange of letters across time.