Margaret "Marnie" Edgar (Tippi Hedren) steals $10,000 from her employer's company safe and flees. She had used her charms on Sidney Strutt (Martin Gabel), a tax consultant, to get a clerical job without references. After changing her appearance and identity, she makes a quick trip to a horse stable in Virginia, where she keeps a horse named Forio, and then to Baltimore for a surprise visit to her mother, Bernice (Louise Latham). Although Bernice seems to care more for a young neighbor named Jessie than she does for her own daughter, Marnie gives her money.