In Hollywood of the 50's, the obscure screenplay writer Joe Gillis is not able to sell his work to the studios, is full of debts and is thinking in returning to his hometown to work in an office. While trying to escape from his creditors, he has a flat tire and parks his car in a decadent mansion in Sunset Boulevard. He meets the owner and former silent-movie star Norma Desmond, who lives alone with her butler and driver Max Von Mayerling. Norma is demented and believes she will return to the cinema industry, and is protected and isolated from the world by Max, who was her director and husband in the past and still loves her. Norma proposes Joe to move to the mansion and help her in writing a screenplay for her comeback to the cinema, and the small-time writer becomes her lover and gigolo. When Joe falls in love for the young aspirant writer Betty Schaefer, Norma becomes jealous and completely insane and her madness leads to a tragic end.
Aspiring filmmakers Mel Funn, Marty Eggs and Dom Bell go to a financially troubled studio with an idea for a silent movie. In an effort to make the movie more marketable, they attempt to recruit a number of big name stars to appear, while the studio's creditors attempt to thwart them. The film contains only one word of dialogue, spoken by an unlikely source.
Outside a movie premiere, enthusiastic fan Peppy Miller literally bumps into the swashbuckling hero of the silent film, George Valentin. The star reacts graciously and Peppy plants a kiss on his cheek as they are surrounded by photographers. The headlines demand: "Who's That Girl?" and Peppy is inspired to audition for a dancing bit-part at the studio. However as Peppy slowly rises through the industry, the introduction of talking-pictures turns Valentin's world upside-down.