John,
Behind That Curtain is something of a hornet's nest among those of us who know about this "Chan Film"!
Technically, it IS a Chan film for two reasons:
1. It's one of Earl Derr Biggers' Chan books of the same name.
2. It DOES have the character of Charlie Chan in it but he comes in late in the movie and half of his involvement in the movie (and when he does get the bad guy) is off-screen.
Behind That Curtain was done over as a romantic story for Warner Baxter, which is just as well since the guy that they hired for Chan was E.L. Parks (a painfully bad actor).
Me? Yes, I have it since I like Baxter and wanted to have all the available Chans available in the series through 1949. I am also a student of films and this movie is during the transition period from silents to talkies.
There is one more reason why I enjoy Behind That Curtain: It also has Boris Karloff in a small but effective role done before he did Frankenstein.
His acting in BTC is better than most of the actors in it and plainly shows why he made the Frankenstein Monster so effective.
Virginia, I think, answered your question fully with regard to "Behind That Curtain." Now, as for Robert Young, he appeears in a prominant role in "The Black Camel." In that film, he is Jimmy Bradshaw, the developing love interest of Julie O'Neil, played by Sally Eilers.