Before and after school, while her parents work, Sonia stays with her next-door neighbour, Mrs. Kaminski, and her granddaughter, Marta. When Sonia accidentally breaks Mrs. Kaminski's precious blue vase, Marta offers to keep it a secret for a price. Sonia is not able to satisfy Marta's escalating demands though - more gifts and more money - and when Marta spreads lies about Sonia at school, her classmates taunt her. Finally, after a teacher discovers stolen property in Sonia's knapsack, Sonia is forced to find the courage she needs to confront her bully.