A friendly group of children spend their summers year after year in a dacha village. They have their own hidden headquarters in a cornfield and a legend that says that not far from the village there is a hidden treasure with the treasures of a princess who fled from Napoleon. When a new girl, Katya, arrives in the village with her mother, she becomes a bone of contention for best friends Sonia and Dashka. But not only friendship will have to pass the test of strength. A certain businessman is going to buy the field with a shalash and organize a construction market in its place. The children decide not to let this happen and after unsuccessful negotiations move to active actions.