In 1914, Germany is arming itself for war. Karl Liebknecht, left-wing revolutionary Social Democrat and workers' leader, a virulent antimilitarist, is one among 110 SPD members of Parliament who vote against approving war loans. From then on, he is considered un-German and a traitor to the fatherland, and his own party's leadership turns against him. Despite threats, Liebknecht speaks up against the war and writes the manifesto The Main Enemy Is at Home. Even when he is arrested and charged with treason, he does not surrender.