Murder, mayhem, and a load of Chinese maxims flood an opera house in San Francisco where a star baritone and a star diva are killed. The police are on the case and they also have asked for the help of Honolulu detective Charlie Chan. This is a real entertaining, fun film to watch. Warner Oland goes through one Chinese proverb after another to remain enigmatic, and yet shed some light on the proceedings. Oland does a nice job as Chan and adds subtlety to not so subtle occurrences. A mad man has escaped from an asylum and has hidden himself within the opera house for reasons unknown to the police. The man is played by none other than the great Boris Karloff. Karloff is a bit restrained in his performance but does add some menace and depth. Watching Karloff sing baritone(with someone's dubbed voice) is quite a sight! Keye Luke is back as Chan's over-eager beaver son. William Demarest plays a somewhat annoying policeman who discredits Chan's abilities really for being an Oriental. The subtle prejudicial undertones of his actions are a bit disturbing. A good script with plenty of humour and lots of Chan!