On the eve of the roundup of the Rome ghetto in 1943, the director of the Fatebenefratelli hospital, Professor Prati, saves several Jewish families by pretending that a contagious virus, known as Morbo K, exists in order to keep the Nazis away. Among the refugees is Silvia Calò, a young artist who falls in love with the doctor Pietro Prestifilippo. While Kappler betrays his promise of salvation and begins the deportations, the destinies of the protagonists intertwine in the most dramatic hours before the departure of the trains.