A baby girl is left at the door of Brady, an Irish-policeman in New York City. He and his friends bid for her, and she is won by Uncle Ben Shapiro, a pawnbroker, who raises her to young womanhood, and is known as Sweet Rosie O'Grady. One day she goes to the rescue of Victor MacQuade, a young man from the high society set, who has been attacked by some east-side gang kids. The next day Victor, dressed as the family chauffeur, calls for her to go on on a ride. He goes home to change clothes while she peeks through the door at a charity costume-bazaar, and is swept inside by some late-arriving guests. She wins first prize for best costume, although she is dressed in the best she has. She flees angry and mortified. Since he has a larger house, she moves to Brady's home, one of her other foster-parents. Victor, who has fallen in love with Rosie, goes to Uncle Ben's shop and asks his permission to marry Rosie.