Cinderella's Twin.

Connie McGill, a scullery maid at the Valentines, dreams of better things. One day, while serving, she sees her Prince Charming, Prentice Blue. Although Blue has nothing but his social standing, the nouveau riche Nathaniel Flint wishes his daughter Helen to marry him in order to gain family status. Flint gives a big party for Helen, which attracts the attention of the Du Geen band of crooks. In a scheme, they furnish the unsuspecting Connie with proper clothes, transforming her, and she ends up at the party dancing with Blue, who is enchanted with her. As she departs, she accidentally leaves her slipper with Blue. Unknown to her, she has aided the crooks in stealing jewels that night, and her slipper contains the key to Flint's safe.