Schoolteacher and family man Ed Avery, who has been suffering bouts of severe pain and even blackouts, is hospitalized with what's diagnosed as a rare inflammation of the arteries. Told by doctors that he probably has only months to live, Ed agrees to an experimental treatment: doses of the hormone cortisone.
Ed makes a remarkable recovery. He returns home to his wife, Lou, and their son, Richie. He must keep taking cortisone tablets regularly to prevent a recurrence of his illness. But the 'miracle' cure turns into a nightmare as Ed starts to misuse the tablets, causing him to experience wild mood swings and, ultimately, a psychotic episode which threatens the safety of his family.