In a South American port, a terrible disease makes its appearance, carried by thousands of rats. Doctor Rieux guesses that the illness is the bubonic plague and gets ready to fight the epidemic. Considering that the best weapons are knowledge and truth, he decides to shed full light on the dangers facing the inhabitants of the city. But the local authorities don't see things in the same way. Worried about public, they install a genuine state of siege with the help of the army. Two french citizens are trapped in this city in quarantine : the cameraman Jean Tarrou and the TV presenter Martine Rambert. Tarrou, a true media man, is determined to cover the event, whatever the danger. Martine is mainly concerned with getting away from the city and, to do so, hires the services of a shady individual, Cottard. In any case, the young people's attitude will be changed by these exceptional circumstances, as well as by the exemplary conduct of Doctor Rieux. The race against time that Rieux and his colleagues have started seems to be on the verge of success, when a series of dramatic and unexpected events occurs...