Eighteen-year-old Nelly lives a quiet life in a small town with her foster mother. There, she makes a living giving piano lessons and letting a room to Ulf, who is in love with her. Despite her financial problems, Nelly's foster mother manages to save enough money to buy Nelly a new dress to wear at a charity ball. However, when Nelly's real mother, Jenny, also buys a dress, Nelly wears this instead. Attracted by the glamorous garment and the promise of a more exciting life, Nelly leaves the small town to join her mother in Stockholm. Once there, she soon discovers that there is a darker side to human nature that she never knew existed when she lived in a small town.