Trapped (1949) is one of those good old noir procedurals, the type that starts with a a little documentary about the Treasury Dept. and all of their works, including protecting us from counterfeit money. It seems that some bogus 20s have been circulating, made from plates made by Lloyd Bridges, now incarcerated. The T-men offer to break him out of prison if he will go undercover to find the counterfeiters. He refuses to be a fink, but they don't give him any choice and break him out. He turns the tables on them, and gets free - or so he thinks. But the feds are on him all the way,
The movie is very hard-boiled, with Bridges never deciding to throw in with the law - he is after the plates for himself and for revenge. He makes a great tough guy with his moll Barbra Payton, shaking down her boyfriend for see money to buy queer money. When the focus shifts to the T-men, it becomes mundane and methodical. They are almost anonymous, but always one step ahead of Bridges.
Sadly, Bridges is sent back to prison before the last act, so the final chase and shootout is less fun than it could have been. But the overall semi-documentary feel with the uncompromising criminality of Bridges makes this a better than average programmer.
But to me, Lloyd Bridges will always be Old Bubblegut, Mike Nelson from Sea Hunt.