Princess Lin Hwa visits Mr. Wong in his home for help, but she is killed by a poisoned arrow. Wong and Capt. Street investigate the murder, and are joined by Bobby Logan, a reporter and Street's fiancée. When they arrive at the princess's apartment to look for clues, they find that her maid has also been murdered. The only witness to the murder is a mute dwarf who mysteriously disappears.
Wong learns that the princess was murdered for the money she brought to buy airplanes for her country. While following a suspect, Wong is captured, but he is rescued by Street and Bobby. The Chinese detective eventually discovers that the murderer is Davidson, the manager of the bank where the princess's money was deposited.