Bill,
There was a Broadway play made of "Keeper of the Keys"
and two movies (okay, a silent serial and a feature film!) made from "House Without a Key." Unfortunately, while both are considered lost, the feature version is among the four that are usually meant when talking about the lost Chan movies.
The other three are also with Warner Oland and include "The Chinese Parrot," "Charlie Chan's Chance," and "Charlie Chan Carries On."
There is another silent serail (also considered lost) that was made from "The Chinese Parrot." It starred Kamiyama Sojin as Chan and George Kuwa, who had played Chan in "House Without a Key."
Among all the other goodies that Rush has here are the scripts to the four "Lost Chans" at http://charliechanfamily.tripod.com/id67.html - or hit the link up there "Return to Website" and go the top of the page. Rush has the link there for the scripts.
You can also check my link for a quickie look at the books and the movies made from them.
