Louis decides he should learn to read and write in order to communicate, and flies away from the refuge to visit Sam Beaver.

When Louis returns to the Red Rock Lakes, he falls in love with a young swan, Serena, but cannot attract her attention.

Instead of accompanying his family north where he might have to face Serena again, Louis visits Sam on his ranch and explains that he feels guilty about the stolen trumpet.

Louis convinces Sam to split one of his webbed feet with a razor blade, making "fingers" so that he can play more notes.

At the end of the summer, he has earned $100, which he carries in a waterproof pouch around his neck along with his slate, chalk, medal, and trumpet.

The zookeeper promises that because Louis is only a guest, he will not be pinioned (have a wing tip cut off to prevent escape) like all the other swans at the zoo.

Louis serenades her by playing "Beautiful Dreamer" on his trumpet, and she falls in love with him, impressed by his song and the numerous possessions hanging around his neck.

Sam goes to Philadelphia and strikes a deal with the Head Man: in every clutch of cygnets, there is always one that needs special care, just as Louis did in his own family.

Louis writes an apology on the slate and gives it and the money bag to his father, who flies back to the music store in Billings.

The book received a strong positive review by John Updike in The New York Times, in which he said, "While not quite so sprightly as Stuart Little, and less rich in personalities and incident than Charlotte's Web – that paean to barnyard life by a city humorist turned farmer – The Trumpet of the Swan has superior qualities of its own; it is the most spacious and serene of the three, the one most imbued with the author's sense of the precious instinctual heritage represented by wild nature.

[5] A "novel symphony for actors and orchestra" was adapted from the book in 2011 by Marsha Norman with music composed and conducted by Jason Robert Brown.

The production starred John Lithgow, Kathy Bates, Jesse Tyler Ferguson, Mandy Moore, James Naughton, and Martin Short.