Cloak and Dagger (1946) review

An agent for the Oh-So-Social (pre-CIA) convinces Professor Jesper (Gary Cooper) to help them stop the Nazis from developing nuclear weapons by sending him to Switzerland to meet a notable scientist forced to work for the Third Reich.  If you can accept Cooper as an expert in frickin' physics (and that's a big "if") and don't mind a romantic subplot involving Jesper and a member of the Resistance (Lilli Palmer) bringing the movie to a screeching halt, this is an above-average spy thriller made with technical assistance from former spook E. Michael Burke.  The backstory might be more noteworthy than what's on screen: there's a fabled "missing reel" with an alternative ending that is probably lost forever and the script was co-written by two members of the Hollywood Ten (which might explain the diatribes about the importance of science).