The plot has as its origin the tumultuous relationship between Hollywood director Mack Sennett and Mabel Normand (transformed from an artist's model to a waitress from Flatbush, Brooklyn for the musical), who became one of his biggest stars. In a series of flashbacks, Sennett relates the glory days of Keystone Studios from 1911, when he discovered Normand and cast her in dozens of his early "two-reelers", through his invention of Sennett's Bathing Beauties and the Keystone cops to Mabel's death from tuberculosis in 1930.