Every Sunday morning during the early 1980's, one of the local channels used to have what they called "Charlie Chan Theater" that ran for an hour and a half.
Still remember the first one I saw: "Charlie Chan's Secret". I remember it well in that it intrigued me not only with it's case, but also the technology (the ultra violet light, the music "repeater" that actually broadcasted on it's own frequency - in 1936, no less!).
That, and it was - and is - the scariest Chan film, IMO. It STILL makes my heart race when I watch it.
And it remains my favorite to this day. Can't watch "Charlie Chan's Secret" unless it's night time and all the lights are turned off.