As noted in the specs, the restored version of this film is 84 min long. I had trouble keeping track of the characters. It didn't help that in the very beginning one character we are introduced to almost immediately puts on a disguise, while another arrives just off a boat and once he shaves his beard looks identical to his brother (played by the same actor). And somehow I didn't catch on that the diamond exchange takes place in the backroom of a seedy bar, so I didn't realize the character called Old Upton (The Jeweler) was the rough-hewn bar owner (Rudolf Klein-Rogge). At least everyone buying and selling jewelry has a beer in front of them. Finally I realized it was a "diamond exchange" -- meaning everyone is fencing stolen or fake merchandise.
Later to add more confusion there is a character the sometimes-disguised husband confesses something to who immediately heads off to blackmail the guy's wife and try to lech on her. Once I figured out who everyone was and what was going on, it wasn't terribly interesting. The twin brother mistaken identity plot is largely just a misdirection to keep things moving and pad out the story. I guess the bad guy gets punished, but getting shot for some mild attempted blackmail seems rather harsh. And it only concerns reputation since the husband knows already, and it seems like it was going to fail since the wife tells the blackmailer to get lost.
It's also a little unclear why a successful broker goes to a seedy underworld bar to buy jewelry for his wife. Or why he's so obsessed with an incident that happened years before.
The seedy/underworld characters are interesting -- a Lang specialty. And there were some rather 1920's touches -- wild hats for the ladies, a big worry about reputation and keeping up appearances (something which has completely gone out the window this millennium after being whittled down for decades), plus casual child labor, and the only black character used as comic relief, making wide rolling eyes and such.
It seems rather minor Lang, but the idea of false appearances, corrupt upper class, a seedy underworld which beckons if you know where to look for it, are themes typical of early Lang films.
