Lady, a pretty Cocker Spaniel from a respectable home, falls in love with the cocky Tramp, a mutt from the wrong side of the tracks. When Lady's master and mistress leave town for a few days, they leave Aunt Sarah and her two wicked Siamese cats to watch the house and care for their baby. The two cats cause trouble for Lady, who is muzzled by Sarah for it. After ending up in the dog pound, Lady is brought home in disgrace and chained outside, but when she sees a rat enter the window of the nursery, she breaks free and causes a ruckus. Hearing the noise, Tramp rushes into the nursery and kills the rat. Although Aunt Sarah is convinced that Lady and Tramp were up to no good, Lady's master returns home and sorts out the events, leading to a well-deserved happy ending.