After schoolteacher Ed Avery (James Mason) faints and is hospitalized, doctors diagnose him with a fatal arterial illness and tell him he has a few months to live. Ed agrees to an experimental treatment with cortisone and makes what appears to be a miraculous recovery. However, upon his return home, his wife, Lou (Barbara Rush), notices severe mood shifts in him. His friend and coworker Wally (Walter Matthau) also perceives the changes, and discovers that Ed has been abusing the cortisone, resulting in his transformation into a household despot.