Deborah Lipstadt, a noted historian and author, fiercely defends the memory of the Holocaust. She is confronted with an academic extremist, a lawyer of controversial theses on the Nazi regime, David Irving, who challenges her to prove the existence of the Shoah. Sure of his fact, Irving assigns Lipstadt to justice, who finds himself in the aberrant situation of having to prove the existence of the gas chambers. How, in remaining within the limits of the law, face a negationist ready for all baseness to win his case, and prevent him from availing himself of this tribune to propagate his nauseating theories?