Paul Muni plays Emile Zola, the French activist/journalist, during his opposition to the Dreyfuss Affair. Zola, already well-known for his muck-raking, had retired from the arenas when the call for help arrived.
In typical fashion, Zola throws himself whole-heartedly into exonerating Dreyfuss, unjustly accused of treason and drummed out of the French army. Although historically questionable, and at some points utterly inaccurate, the story is a morality play about the importance of standing up to the Establishment when you know they're wrong.
I expected to slog through this movie and was happily surprised. I wouldn't rate it in my top 100, but I'm glad I saw it.