How far have scientists advanced toward solving the riddle of cancer, and what are the key problems now facing them? To explain the enormous complexity of the problem, the film traces briefly the growth and multiplication of a single fertilized cell into an adult man, and asks why some outlaw cells begin persistent growth after the whole body has reached maturity. Research scientists are shown following up clues with test tube, microscope, controlled diets and other aids that may guide them to the eventual solution. Methods of treatment being used meanwhile for different types of cancer are briefly described. As each new aspect of the disease is revealed, the secret of cancer is seen to be as complex as the universe itself, and the quest for its solution one of the greatest adventures on which a scientist can embark.