Just a guy who lost his job and couldn't replace it because of pride, cheated on his wife (maybe with multiple women?), and maybe became homeless?
For anyone who doesn't already know the story, I think it's best to go in blind, but if you don't mind spoilers (and I guess this one has definitely reached the statute of limitations):
"Cheever's swimmer is a tragic hero disguised as an upper-class suburbanite. There are a lot of tragic heroes hidden in suburbia, I guess, perhaps because so many of them subscribe to the New Yorker."
The story is allegory. The movie uses cinematic techniques to enhance the presentation and the acting is of high quality.