Sunset Trail (1938)

Keller buys Marsh's cattle and then murders him to retrieve the money. But Ann Marsh remembered some of the serial numbers and this is the clue that Hoppy needs. He arrives posing as a dude. He also poses as a novice poker player and this brings in a few of the stolen bills. When he realizes Keller is the one he is after, he wins back all the money at the poker table. He escapes from Keller's saloon but Keller and his men head out after him.