The Clouded Yellow. A 1950 movie starring the great actor, Trevor Howard. The ending is quite good with a surprise (to me) twist. Quite suspenseful.
https://www.echelonclassicfilms.com/the-clouded-yellow.html
Cloudburst. A 1951 movie starring Robert Preston. I would classify this movie as a "film noir". I would recommend watching, first, without looking up the detailed plot. I found it to it to be a quite "slow" movie but it is worthwhile to stick with it and watch it to the end.
I found the movie attractive since it involves a post WWII code breaker, espionage, lead character.
Try and do a search for the title on Google. You will get some listings were the movie has been taken down due to copywrite, but I found other listings were the movie was still available, on YouTube.
I like espionage movies. I wonder how many people come to the PLUG forums just to get movie ideas from you, Bill. I have to figure out how to gather and review stats on the new host but I hope soon to be able to find out stuff like that.