Finishing school student Marcia Bradburn, Donna Reed, brings good news to her boyfriend Roy Todwell, [Phil Brown], as her father approves their engagement. Yet when she refuses to elope immediately, Roy’s temper flares in a shocking act: he grabs a flagstone and cruelly kills his dog, then drives off into the night.
Emma Hope, [Mary Nash], the head of the school, calls in her longtime friend Dr. Gillespie, [Lionel Barrymore], who then brings in Dr. John Hunter Gerniede, [Philip Dorn], a surgeon who has long pursued the idea of becoming a psychoanalyst. Gerniede conducts a covert examination of Roy without Roy’s knowledge and reaches a stark diagnosis: dementia praecox. The doctors urge treatment in a mental institution, but Roy’s parents place their faith in the family physician, Dr. Ward O. Kenwood, [Charles Dingle], who insists their son is simply overworked at college and needs rest. Kenwood remains steadfast even after Roy suddenly erupts again, tearing apart a toy store display during an outing with Marcia, and locking Roy away for the night out of caution.
Roy escapes through a window, and, convinced Gillespie is his enemy, starts sending threatening postcards from various cities. In one stop, Roy purchases a car and, when it is delivered, murders the entire sales team involved in the purchase. When Marcia later glimpses Roy on school grounds, Gillespie is placed under police protection, but the hospital is vast and difficult to secure. Roy slips in undetected, kills Kenwood’s assistant, and masquerades as him, triggering a tense cat-and-mouse chase through the institution. As Roy reaches out to Marcia, she manages to calm him enough to get him to come in, and, for a moment, seems to have coaxed him back toward a sane interpretation of his life.
Back in Gillespie’s office, Roy, in a still moment of supposed clarity, pulls a hidden gun from Gillespie’s desk and declares that he must kill the doctor to be cured. The plan backfires when a hospital attendant—Nat Pendleton—emerges from the next room and, with a swift wrench, knocks the weapon from Roy’s grasp, ending the immediate danger. Roy is soon sentenced to the penitentiary, and in a closing scene, Gillespie visits Marcia only to find that she has a new partner, a soldier, suggesting life goes on beyond the crisis.
