A gangster is killed by a big man who pays no attention to bullets, and who leaves glowing fingerprints. Police scientist Chet Walker (Richard Denning) discovers that the fingerprints are radioactive -- as well as those of a dead man.
We soon learn that this walking corpse was created by Dr. Wilhelm Steigg (Gregory Gaye); he's allowing secretly-returned deported gangster Buchanan (Michael Granger) to get revenge on those who were responsible for his conviction.
Steigg removes part of the brains of recently-dead men, and replaces them with a device that allows them to control the body from a distance, like a robot; they can even see through the creature's eyes via television.
Another atomic zombie kills the district attorney who convicted Buchanan, which leads Chet and his homicide detective friend Dave Harris (S. John Launer) to deduce that the killings are connected to the Buchanan case. Warnings are issued to other possible targets, but they're unable to prevent another death. The last two go into hiding.
The movie concludes with a headline: Creatures with the Atomic Brains Destroyed. This entertaining but cheesy little movie is completely unpretentious.
Broad, surprisingly gruesome and well-paced, it's obviously aimed straight at the juvenile market -- and it hits it, too. A sterling artifact of its time: brisk, efficient and entertaining, even if it is awfully silly.