Managing editor James Manning saves Mona Gould from attempted suicide, and after discovering that she is a destitute writer, he hires her to write for the Tribune . He assigns reporter Eddie Morgan to investigate Chinese immigrants entering San Francisco illegally. Having previously lived near Chinatown, Mona secretly follows Eddie. She is familiar with many of the locals, including Miao Lin, whose guardian, Wu Sin, will not allow her to marry Charlie San, a young bank employee. Always one step ahead of Eddie, Mona discovers that the smugglers bring people in on the ship Hirondella and transfer them to a private truck. Mona hires a detective who finds out that the Hirondella is owned by millionaire Roger King, whose daughter Margaret is engaged to James. Mona goes to Margaret to warn her of her father's illegal dealings, but Margaret refuses to believe her. Margaret informs her father, who asks Wu Sin for protection. Wu Sin, head of the Tongs, manages the entry of the illegal immigrants. He calls a meeting of the Tongs, who choose Charlie San to kill James. Charlie is horrified by his assignment, but he agrees to do it when Wu Sin says his reward will be marriage to Miao Lin. A newspaperman through and through, James agrees to print the story about Margaret's father even though it means losing his engagement to Margaret. Miao Lin confesses to Mona about Charlie's assignment, and when Mona and James go to Mona's apartment one night, he is shot by Charlie. He receives only a flesh wound, however, and because Mona knows Charlie's story, they understand his motives. Police discover Wu Sin dead in his home. Roger King and Margaret leave on the Hirondella . After Charlie San is granted probation, he and Miao Lin marry, while at the same time, James and Mona marry, after having finally acknowledged their love for each other.