***SPOILERS*** Real life pacifist Lew Ayers plays Dr. Tom Clay a man who's dream is to invent a cobalt bomb that's so destructive that it would make future wars and conflicts totally obsolete. Dr. Clay is so determined to make the bomb workable that he neglects his wife Joanne, Julie Adams, and his good friend and house guest author Robert Blake, Robert Webber, spending all his time in his study working on it. Tom is so carried away with his project, the cobalt bomb, that he doesn't realize that Joanne and Robert are having a secret affair right under his nose and in his house. But what's even more serious then a run of the mill illicit affair that Robert and Anne are having is that Robert is also a paid spy for the Soviet Uniion and planning to steal Tom's secret blueprints for his cobalt bomb!
It's later when Tom takes his top secret papers-File 281-on the cobalt bomb home that Robert sees his chance to secretly photograph it and send the film together with himself to his Soviet contacts in Mexico City. While all this is happening Robert in planning to knock off two birds with one stone by talking Joanne to get on the plane with him and leave her husband, who can't seem to find any time with her, and get a both divorce from Tom and marry him. Tom who had caught Robert red handed stealing his top secret blueprints is blackmailed by him in that he himself had broken security at the research plant by taking the blueprints homes without proper authorization.
***SPOILERS*** With his wife about to leave him and now facing a possible jail term for breaking security Tom in first attempting to buy the blueprint film off Robert is then forced to pull a gun on him to prevent him from taking off at a local airfield, this time without Joanne, for Mexico City! Robert in knowing how Tom is against violence of all types still turns and pulls his own gun out on him. And before Robert can get a shot off Tom, without thinking, blasts him away. It was Tom's loyalty to his country that in the end made him do what would have been totally unthinkable for him to do. But it was Robert's actions in pulling a gun on him as well as being a Soviet spy who was about to give the Soviet Union the most destructive weapon in all of human history,the cobalt bomb, and who were more then willing to use it that made Tom the lifetime pacifist for just one split second turn violence.
P.S Check out Leonard Nimoy as US Government Agent Cowell who's job it is to see that nothing happens to Tom and ends up together with his partner Agent Chester,Morgan Jones, preventing the getaway plane without Robert Blake, who was by then shot by Tom , but with his roll of film about the cobalt bomb from taking off.