Journalist Johnny Barrett (Peter Breck) thinks that the quickest way to a Pulitzer Prize is to uncover the facts behind a murder at a mental hospital. He convinces an expert psychiatrist to coach him to appear insane; this involves relating imaginary accounts of incest with his "sister", who is impersonated by his exotic-dancer girlfriend (Constance Towers). Barrett convinces the authorities and is locked up in the institution where the murder took place. While pursuing his investigation, he is disturbed by the behavior of his fellow inmates.
The film starts as David Clemens (Keir Dullea) is brought to a residential treatment center by his apparently caring mother. He becomes very upset when one of the inmates brushes his hand, as he believes touches can kill him. Cold and distant, he mainly concentrates on his studies, especially that of clocks, which he appears to be obsessed with. We later learn that he has a recurring dream in which he murders people by means of a giant clock.
1928 Kansas: Wilma Dean "Deanie" Loomis (Natalie Wood) is a teenage girl who follows her mother's advice to resist her desire for sex with her boyfriend, Bud Stamper (Warren Beatty), the son of one of the most prosperous families in town. In turn, Bud reluctantly follows the advice of his father, Ace (Pat Hingle), who suggests that he find another kind of girl with whom to satisfy his desires.
New Orleans, 1937: Catherine Holly (Elizabeth Taylor) is a young woman institutionalized for a severe emotional disturbance that occurred when her cousin, Sebastian Venable, died under questionable circumstances while they were on summer holiday in Europe. The late Sebastian's wealthy mother, Violet Venable (Katharine Hepburn), makes every effort to deny and suppress the potentially sordid truth about her son and his demise. Toward that end, she attempts to bribe the state hospital's administrator, Dr. Lawrence J. Hockstader (Albert Dekker), by offering to finance a new wing for the underfunded facility if he will coerce his brilliant young surgeon, Dr. John Cukrowicz (Montgomery Clift), into lobotomizing her niece, thereby removing any chance that the events surrounding her son's death might be revealed by Catherine's "obscene babbling.
This is a story of a nurse in a psychiatric hospital, played by Suchitra Sen. Sen's character is a part of a team exploring new therapy for patients who have suffered emotional trauma. The approach taken by the team is to offer these individuals an emotional resort, which is where Sen's character plays her part. Her role is to act as a friend and a lover for the patient, but at the same time, refrain from any emotional involvement on her own part as her role is purely that of a nurse who is helping the patient recover. She has to repeatedly break the emotional attachments that she experiences because as a nurse, she is a part of therapy.
François is committed to a mental hospital by his father Maître Gérane, a wealthy man who does not tolerate objection. The institution is owned by Dr. Varmont whose traditional treatment methods conflict with the beliefs of Dr. Emery, supporter of a more sensitive approach. François becomes friends with an epileptic, Heurtevent and together they try to escape, but they fail and the sweet Heurtevent commits suicide. Afterwards François manages to flee and hides at the home of his friend, Stéphanie.
The plot concerns a doctor at a run-down psychiatric hospital, who is offered a large sum of money to shelter a new patient. Soon the place is full of suspicious and secretive characters, all apparently international secret agents trying to find out who and what the patient is.
Le professeur Charles Conway est un savant fou qui espère découvrir le secret de la jeunesse éternelle en faisant des expériences sur des glandes situées dans le cerveau. Il utilise comme cobayes des personnes dépressives, sans familles et sans attaches, qui pensent être soignées pour leur dépression. Toutefois, les expériences du Pr. Conway tournent mal et ses cobayes deviennent des sortes de zombies…
Dr. Stewart McIver (Richard Widmark) is now in charge of a psychiatric facility, one run for many years by medical director Dr. Douglas Devanal (Charles Boyer).
Successful stage director Jim Downs (Ferrer) is driven to a mental breakdown by his domineering wife Ann (June Allyson). Institutionalized, he confides in Dr. Bellman (Kendall Clark) and Dr. Barrow (Isabel Bonner), and he finds a kindred spirit in Charlotte Moore (Joy Page).
Cheryl Draper (Barbara Stanwyck), while looking out her bedroom window, witnesses a young woman being strangled to death. The woman reports the killing to the police, but when the man named Albert Richter (George Sanders) notices detectives arriving downstairs, he moves the body. When the police show up to his door, Richter acts nonchalant, and when no body is found, the police are convinced that the woman saw something in her dreams.
Elwood P. Dowd (Stewart) is a middle-aged, amiable (and somewhat eccentric) individual whose best friend is an invisible 6' 3.5" tall rabbit named Harvey. As described by Dowd, Harvey is a pooka, a benign but mischievous creature from Celtic mythology who is especially fond of social outcasts (like Elwood). Elwood has driven his sister and niece (who live with him and crave normality and a place in society) to distraction by introducing everyone he meets to his friend, Harvey. His family seems to be unsure whether Dowd's obsession with Harvey is a product of his (admitted) propensity to drink or perhaps mental illness.
Virginia Cunningham (Olivia de Havilland) is an apparently schizophrenic inmate at a mental institution called the Juniper Hill State Hospital. She hears voices and seems so out of touch with reality that she doesn’t recognize her husband Robert (Mark Stevens).