Frank Baturin, called "The King of Chinatown," has all the rackets in the palm of his hand. After Baturin loses $20,000 in a benefit boxing match, he hires hit man Rep Harrigan to kill his rival, Mike Gordon. Gordon has won the loyalties of Baturin's lieutenant, an ex-convict called "The Professor," however, who orders Rep to warn Gordon instead of killing him. As a result, Baturin is shot by Gordon in front of a pharmacy owned by Dr. Chang Ling, who refuses to join the Merchant's Protection Association, which has been extorting money from the local merchants. Baturin is found by Ling's daughter, Dr. Mary Ann Ling, who, believing that her father shot the racketeer to stop his threats against the Chinese merchants, comes to the aid of the wounded man. Because of Baturin's extended convalescence, Mary is forced to relinquish her fundraising activities to establish a Red Cross nursing unit in war-torn China. During his weeks of recovery, Baturin falls in love with Mary, despite her involvement with lawyer Bob Li, and is determined to reform. Although the Professor had hoped to succeed Baturin in running the mob, Gordon takes over, and a reign of terror follows in Chinatown. The Professor visits Mary to try to intimidate her into allowing Baturin to die or else her father will be killed. Learning of the Professor's threats to Mary, Ling hires an attorney to frame the Professor. Rep then tells Mary that Gordon was Baturin's would-be assassin. When District Attorney Phillips confronts the Professor, he names Gordon as Baturin's attacker, and Gordon confesses. Meanwhile, Ling visits Baturin's to take Mary home, and she hopes to convince Ling that Baturin is a reformed man. Rep then calls Baturin to warn him that the Professor is en route to his home to kill him and Ling. Baturin successfully disarms the Professor, but is mortally wounded. The police then arrest the Professor. Before dying, Baturin bequeaths Mary a healthy endowment for her nursing unit. She marries Bob and leaves for China, secure in the knowledge that her father had no hand in the violence.