The major difference between the play version of Sweet Bird of Youth and the movie version is the ending. Unlike the staged version of the play, the movie got the typical Hollywood happily-ever-after ending. In the movie, the boy gets the girl and they disappear into the sunset (or moonlight),...
with the audience’s understanding that they will live happily ever after.
This is not what happens in the play. The story centers on protagonist Chance Wayne, who is portrayed in the movie by Paul Newman. He is a ne'er-do-well who relied on his good looks to travel to Hollywood in pursuit of a career as a movie star. Needless to say, he never made it in films and now his looks are fading. He supports himself as a two bit gigolo, engaging in short-term affairs with a series of older women who support him and give him money.
He returns to his southern hometown with one such woman, Alexandra Del Lago. Just as Alexandra Del Lago mourns her lost youth, Paul Newman’s character is getting too old to be the perennial gigolo and this is his last chance at happiness. Chance's hometown sweetheart, Heavenly Finley, still lives there in the home of her domineering, tyrannical and oppressive father, Boss Findley.
Boss Findley not only runs his family but, as one of the wealthiest locals, most of the town itself. Both the play and the movie center on this trip as Chance’s last opportunity for redemption and to finally win the girl for whom he has yearned all these many years.
Heavenly turns Chance down in the play, refusing to run away with him. Instigated by her vengeful father, Heavenly’s brother Tom and his friends go after Chance to attack and possibly castrate or kill him. This kind of violent ending was too much for a film, which had to be put before the film rating agency. Thus, the ending was changed for the movie and Heavenly does run away with Chance.
The last scene in the movie shows Heavenly and Chance, as well as Alexandra Del Lago, driving away from town. By comparison, in the play, Alexandra, whom Chance calls Princess, urges him to leave with her but he refuses to go. Heavenly’s brother Tom Junior “enters from steps, pauses, and then gives a low whistle to” his friends, who appear on stage presumably to do harm to Chance. This ending is much more difficult and sad than the movie version. Chance has the final words, which he speaks presumably to the audience:
I don't ask for your pity, but just for your understanding—not even that—no. Just for your recognition of me in you, and the enemy, time, in us all.