Following a case in London, Charlie Chan (Warner Oland) flies to Paris pretending to be on vacation, but he is actually on a mission to investigate a bond-forgery racket. But his agent, apache dancer Nardi is killed by a mysterious beggar before she can tell him anything. Returning to his hotel room Chan is pleasantly surprised to find number one son, Lee (Keye Luke) waiting for him. Together, they take on the sinister case. The case, complicated by a false murder accusation for banker's daughter Yvette, climaxes with a strange journey through the sewers of Paris.