Once there lived a little girl named Desi who was only three years old when her father died. Desi's mother move to live with her parents. Desi doesn't understand what has happened as she is not very well aware of the circle of life and only refers to herself in the third person. Desi's grandmother has the idea of helping Desi write a letter to her father. They leave the letter at her father's grave, and every day Desi waits for the postman to bring her a reply. However, when the letter is returned to them, Desi's emotional and mental state worsen. Desperate, Desi and her mother go to the carnival with a local pilot, where Desi is given a balloon with a picture of a mermaid on it. Desi's grandmother has the idea of attaching a letter to the balloon and sending it to Heaven.

4000 miles away, a man duck hunting on the Mermaid River outside the town of Mermaid finds the balloon. Touched by Desi's letter, he and his wife reply. Upon receiving their letter, Desi begins to recover and the two families form a bond.