A modest and plain young Małgorzata leads a very boring life as a cashier. One day a robber riddles her bank car with bullets, kills driver and two security guards and takes the money. The police finds out that the stolen banknotes are being spent at a fashionable spa resort. The only way to find the criminal is to favor Małgorzata with a seaside holiday in the company of a handsome Captain as her "brother"...