His song "Deep Dreams" is a big hit circa 1926. Big enough for him to quit boxing, date Stella Graham, buy a lotta expensive stuff and then run outta money. He thinks he can just write another hit song, but his follow up, "Sweet and Hot," can't get any traction with the music publishers, and he has to go back to boxing. Stella goes back to dating Charlie Ellsworth and sends Johnny a "Dear John" letter on the eve of his lightweight championship bout. Distraught, he loses and gets injured badly. Stella marries Charlie for two years, but he turns out to be a drunken wife-beater.
Then Stella sees on the paper that Johnny's in the hospital on his deathbed.