Captain Flash was Keith Spencer, a science professor who lived in Atom City, a municipality located somewhere in western United States. As the name implies, lots of atomic research went on there. One day, Keith Spencer was a teaching a class when an experiment with radioactivity went horribly wrong. Keith bravely shielded his students with his own body, absorbing all the radiation. Although he survived the experience, he knew that the radiation would eventually kill him and prepared for a slow, painful death.