Behind That Curtain

As others have noted, this film is very dull. This is largely due to the extremely slow delivery of actor Gilbert Emery, who plays Sir Frederic Bruce of Scotland Yard. You can almost sense the impatience of the other actors whenever he's onscreen. If you're only curious about Charlie Chan, skip to the last 10 or 15 minutes.

According to THE FILMS OF BORIS KARLOFF, by Richard Bojarski, this was released in both sound and silent versions (a common practice during the early years of sound films). It would be interesting to see if the silent version, running at a faster film speed, is less dull.