When research scientist Dr. Gilbert "Gil" McKenna (Clarke) falls unconscious after accidentally being exposed to radiation during an experiment with a new radioactive isotope, he is rushed to a nearby hospital. Attending physician Dr. Stern (Robert Garry) is surprised to find that Gil shows no signs of burns typical for five-minute exposure to radiation and informs Gil's co-workers, lab assistant Ann Russell (Patricia Manning) and scientist Dr. Frederick Buckell (Patrick Whyte), that he will keep the patient under observation for several days.