Charlie Chan at the Opera is considered by many to be the best Warner Oland Charlie Chan film, probably due to the presence of Boris Karloff as the principal suspect, as well as faux operatic music composed by Oscar Levant. This is the 13th film starring Oland as Chan; it was directed by H. Bruce Humberstone for 20th Century-Fox in 1936.

Plot

Charlie Chan (Warner Oland) gets a chance to watch a popular opera performance. For seven years, opera star Gravelle (Boris Karloff) has been locked in an insane asylum, his identity a mystery – even to himself. But when his memory unexpectedly returns, he begins to recall that his wife and her lover tried to murder him – and now he's determined to make them face the music. Gravelle escapes from the asylum and makes his way to the San Marco opera house and begins hiding out in the various rooms and passageways. Soon, members of the opera company are being murdered one by one.

Source: Wikipedia