Calm office worker Anthony, son of an American father and a Japanese mother, lives in Tokyo with his wife Yuriko and their little son Tom. Since Anthony's mother died of cancer, his scientist father has been overly fearful for their health and rigidly subjects Anthony and Tom to monthly physicals. Walking home, Tom is killed in a hit and run before Anthony's eyes. Losing their boy pushes Yuriko over the edge and triggers violent emotions in Anthony, whose body begins to transform. Little by little, his cells turn into iron. When the driver who killed Tom reappears and Anthony learns the truth about his father's past experiments on human guinea pigs and about his mother's death, Anthony mutates into a mass of metal - a human weapon fuelled by an uncontrollable rage.