Fresh graduate Pavel Tomás (Juraj Durdiak) enters a job as an assistant in a district town's public health office. As the health officials pass the river Kamenice, Pavel notices large patches of foam on the water surface, and the river also has an unpleasant smell. Pavel's superior Dr Slivenec (Václav Voska) is a nice and talkative man, but the suggested radical solutions to the violations of public health norms are greatly diluted after a phone-call is made by somebody influential who calls on behalf of the offender.