After years of hopeful struggle, Al Stone (Jolson) is on his way. "I'm Sittin' on Top of the World", he sings to an appreciative speakeasy crowd. But, as Al discovers, getting there is one thing. Staying there is another. Singing waiter Stone gets his huge break on a magical night when his song wows a big-time producer and a gold-digging showgirl he fancies. Broadway success and marriage follow, but sure enough, hard times are on the way. Al's fickle wife abandons him, taking the beloved son he calls Sonny Boy with her. Heartbroken, Al becomes a devastated loner until friends from the speakeasy that launched his career rescue him from a life on the streets. Soon, Al is back in lights. But another crisis awaits: Sonny Boy is in the hospital and dying....