Engineer Sodoma (Vladimír Hrubý) and his colleague Vera (Jana Stepánková) are busy making the last tests of their invention - a miniature radio-telephone which is built into a powder-compact on one end and into a cigarette case on the other. A gang of criminals want to steal the invention and to sell it abroad. Their intentions are marred by a group of children who play on detectives at the local country fair.—NFA.cz