Sandra Bullock stars as Dr. Kate Forster, who moves from the suburbs of Illinois to Chicago.

Before leaving the beautiful house she was renting, she decides to leave a note for the next tenant, asking them to forward her mail to her new address, apologizing with a footnote that the dog paw prints they will see at the door were there before her move.

The new tenant is Keanu Reeves, who plays the multi-talented architect Alex Wyler. Initially, Alex is indifferent to the letter he finds. However, after a strange incident, he begins to correspond with Kate.

The correspondence that starts on a friendly level will soon turn into a passionate "letter" romance. The two lovers, however, face a very significant problem.

In order to meet in person, they must break through time as they live in different moments in time...