Mr. Moto (Lorre) is teaching a class for would-be sleuths and one of his students is Charlie Chan's son, Lee (Luke), who helps out when Moto investigates the murder of a boxer during a fight. Originally intended as a Charlie Chan film that was already in production, the script was rewritten because of Warner Oland's health problems and doesn't quite fit the other Moto adventures. 3rd in the series.