Set in the mid through late 19th century, it depicts Zola's friendship with Post-Impressionist painter Paul Cézanne, and his rise to fame through his prolific writing, with particular focus on his involvement late in life in the Dreyfus affair.
Struggling writer Émile Zola (Paul Muni) shares a drafty Paris attic with his friend, painter Paul Cézanne (Vladimir Sokoloff). A chance encounter with a street prostitute (Erin O'Brien-Moore) hiding from a police raid inspires his first bestseller, Nana, an exposé of the steamy underside of Parisian life.
Other successful books follow. Zola becomes rich and famous; he marries Alexandrine (Gloria Holden) and settles down to a comfortable life in his mansion. One day, his old friend Cézanne, still poor and unknown, visits him before leaving the city, and tells Zola that with his success he has become complacent, a far cry from the zealous reformer of his youth.
Meanwhile, a French secret agent steals a letter addressed to a military officer in the German embassy. The letter confirms there is a spy within the top French army staff. With little thought, the army commanders decide that Jewish Captain Alfred Dreyfus (Joseph Schildkraut) is the traitor, is courtmartialed and imprisoned on Devil's Island in then French Guyana.
Later, Colonel Picquart (Henry O'Neill), the new chief of intelligence, discovers evidence implicating the spy as Major Walsin-Esterhazy (Robert Barrat), but he is ordered by his superiors to remain silent to avert official embarrassment and is quickly reassigned to a distant post.
Years go by. Finally, Dreyfus's loyal wife Lucie (Gale Sondergaard) pleads with Zola to take up her husband's cause. Zola is reluctant to give up a comfortable life, but she brings forth new evidence to pique his curiosity. A letter is published in the newspaper accusing the army of covering up the monstrous injustice. Zola barely escapes from an angry mob incited by military agents provocateurs.
As expected, he is brought up for libel. His attorney, Maitre Labori (Donald Crisp) does his best against the presiding judge's refusal to bring up the Dreyfus affair and the perjury committed by all the military witnesses, except for Picquart. Zola, found guilty and sentenced to a year in prison, reluctantly accepts his friends' advice to avoid risk becoming a martyr and instead flee to England, to continue the campaign on behalf of Dreyfus.
A new administration finally admits that Dreyfus is innocent, those responsible for the coverup are dismissed or commit suicide, although Walsin-Esterhazy flees the country in disgrace. Zola dies of accidental carbon monoxide poisoning due to a faulty stove the night before the public ceremony in which Dreyfus is exonerated.
Contemporary reviews were unanimous in their praise. Frank S. Nugent of The New York Times wrote, "Rich, dignified, honest, and strong, it is at once the finest historical film ever made and the greatest screen biography, greater even than The Story of Louis Pasteur with which the Warners squared their conscience last year ... Paul Muni's portrayal of Zola is, without doubt, the best thing he has done." Variety called it "a vibrant, tense and emotional story ... It is finely made and merits high rating as cinema art and significant recognition as major showmanship." Harrison's Reports called it "A dignified, powerful, and at times stirring historical drama, brilliantly directed, and superbly acted by Paul Muni, as Zola, the great French writer." John Mosher of The New Yorker praised it as "a picture of considerable distinction" with "no nonsense." The Life of Emile Zola topped Film Daily's year-end poll of 531 critics as the best film of 1937.
Certain scenes have been interpreted in the context of the time as a reaction to the increasing repression of Nazi Germany. Critic David Denby in 2013 noted that, while the movie featured progressive rhetoric in Zola's last speech, overall it was "a perfect example of the half-boldness, half-cowardice, and outright confusion that marked Hollywood's response to Nazism and antisemitism in the nineteen-thirties." For instance, the film never mentioned "antisemitism" or "Jew". In 2013 American scholar Ben Urwand reported that studio head Jack L. Warner, a Jew himself, personally ordered the word 'Jew' to be excised from all the dialogue in the film, although Urwand's thesis of collaboration with the Nazis is strongly disputed by the movie mogul's families, especially Alicia Meyer, who also disputes that such an order was given.
The film is among the subject films studied in two books published in 2013: Ben Urwand's The Collaboration: Hollywood's Pact with Hitler, and Thomas Doherty, Hollywood and Hitler, 1933-1939. Denby notes that Doherty provides more context for the studios' behavior, setting it against the political culture of the period. Urwand learned that Georg Gyssling, the Nazi consul in Los Angeles, occasionally was allowed to review and make recommendations on films. But, in the same period, the studios set up an association office to develop a Production Code, directed by Will H. Hays, who appointed a Catholic layman, Joseph I. Breen as "censor-in-chief," who after 1934 had even more influence over movies. Denby found the studio heads acting as businessmen, who were sometimes overcautious and fearful of their place in American society.