In revolution-torn China, American mercenary O'Hara (Gary Cooper) is entrusted with a perilous mission, to get arms for the helpless authorities in a province ravaged by warlord General Yang (Akim Tamiroff). On the train to Shanghai, he meets Judy Perrie (Madeleine Carroll), whose father is in league with Yang. Will Judy regret agreeing to lure O'Hara to his doom, and if so, can she make it up to him? The balance of power seesaws to a perilous conclusion.