It is a dark and stormy night and at a certain sanatarium for mental patients one of the inmates is, as ever, playing the piano and singing opera at the top of his voice. His attendant walks in to give him the newspaper and warns him if he doesn't stop singing he won't offer this service for him anymore, but the patient is distracted by a photograph on the front page. It is a picture of the opera performer Lilli Rochelle (Margaret Irving) who he immediately recognises and when he does he finds the amnesia that has plagued him for years is lifting. The patient is in fact Gravelle (Boris Karloff), an opera singer who was believed dead in a theatre fire, and now his shattered mind wants revenge. He knocks out the attendant, and escapes to Los Angeles with murderous intentions - can Charlie Chan (Warner Oland), the famed detective, stop him?
Charlie Chan at the Opera is considered by many to be the finest of the sleuth's screen series, certainly the best of the Oland efforts, and it is blessed with a true horror star, Karloff, as its villain, although it's not really a horror film. Karloff seems to be enjoying himself here, going over the top to entertaining effect, whether he's lip synching to the opera (which was "Carnival" by acerbic celebrity pianist Oscar Levant) or skulking round the corridors of the theatre. That theatre is mainly the location the story centres on, substituted for a "country house from which no one can escape" mystery that you might expect from these films. As usual, Chan is the smartest guy in the room, speaking in aphorisms and figuring out what is actually going on way before anyone else, with help from Number One Son Lee, played by Keye Luke in one of the few non-stereotypical East Asian roles in the Hollywood of the day.
Yes, Chan as the Confucius-spouting wise man was a cliché, but at least he's the hero, and by the end everyone looks up to him - even the murderer has a grudging admiration for him. We think the killer will be Gravelle as, despite a police manhunt, he has not been tracked down, and he has turned up at the theatre where he wants to play Mephisto which will give him the opportunity to bump off his wife when the onstage murder becomes a real one. He manages to carry this off, but is he responsible for the other killings that night? Only Chan knows for sure and with the help of Lee he will work out the truth. There are plenty of nice moments to show that you shouldn't take all this too seriously, with the stage manager not caring if "Frankenstein himself" turns up, the show must go on, and the policeman who tells the cast they must stay and perform despite the sinister events offhandedly calling them "you hams". The mystery is nicely plotted by Charles Belden and Scott Darling from Bess Meredyth's story and draws to a satisfying close, but it's a pity Oland and Karloff don't have more scenes with each other. Watch for the primitive but then state of the art way Gravelle's photo is sent cross country.