After a terrorist attack against a train, the police arrest the young laborer Stefano Baldini, member of a group of militant leftists. Entrusted for interrogation to Sergeant Pendicò and special agents Lorusso and Spasiani, Stefano dies, after four days, in unclear circumstances. Doubting the official version of the police, the second time in which a young person died in custody, journalist Cristina Visconti tries, with the aid of the sister of Stefano, to discover the truth. They rub up against a conspiracy of silence that encircles the acts of Pendicò and his associates. Frustrated beyond reason, Cristina tries a desperate ploy: publishing a story without evidence in the newspaper, accusing the three agents of having caused the death of Stefano with their blows. Cristina is put on trial for defamation. Can she avoid going to jail and also reveal the facts surrounding Stefano's death?