New Orleans, 1937. Catherine Holly (Elizabeth Taylor) is a young woman institutionalized for a severe emotional disturbance that came about when her cousin, Sebastian Venable, died under questionable circumstances while they were on holiday in Spain a few months earlier. The late Sebastian's wealthy mother, Violet Venable (Katharine Hepburn), makes every effort to deny and suppress a potentially sordid truth about her son and his demise. Toward this end, she attempts to bribe the state hospital's administrator, Dr. Hockstader (Albert Dekker), by offering to finance a new wing for the underfunded facility (in Sebastian's name) 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".Mrs. Venable meets with Dr. Cukrowicz in the primordial garden ("like the dawn of creation") at her estate to discuss her niece's case, and their conversation eventually turns to Sebastian. Mrs. Venable describes him as a poet whose art was his sole occupation... even though he only wrote a single poem each year during the summer months and never published his work... and recounts her own previous vacations with him and of the poems that he kept in a poetry book that she reads from time to time. Mrs. Venable then reads out loud to Dr. Cukrowicz one poem from the book which tells of one particular voyage to the Encantadas a few years ago where her son forced her to witness the horrific sight of birds feeding on newborn turtles emerging from the sand, a ghastly scene in which Sebastian believed he saw the "face of God".Cukrowicz agrees to visit Catherine and begin his evaluation. Catherine has been confined to a private women's mental institution since her return from Europe several months earlier. At first remaining out of sight, Cukrowicz watches as she is caught smoking by Sister Felicity (Joan Young), one of the nuns who staff the facility. When the nun confronts Catherine and holds out her hand, demanding that she turn the cigarette over, Catherine responds by extinguishing the lit cigarette into her palm, burning her. The nun then tells the doctor that this can be seen as proof of her mental instability. Cukrowicz dismisses Sister Felicity and goes on to interview Catherine in her room. She claims that her memory does not extend any further back than an incident that occurred just before she left for Europe with Sebastian, when she "lost her honor" while being driven home from a Mardi Gras ball. Beyond that, she struggles to recall the events that led to Sebastian's death and her subsequent breakdown, but expresses her desire to do so.Beginning to doubt that she has lost her mind, Cukrowicz decides to move Catherine into the state hospital for continued observation. Catherine's mother (Mercedes McCambridge) and brother George (Gary Raymond) pay her a visit and reveal that Sebastian has left them a considerable sum of money in his will. Unfortunately, Mrs. Venable will not give them the inheritance unless they sign papers to commit Catherine to the institution and allow a lobotomy to be performed. Alarmed by this prospect, Catherine tries to escape. She accidentally wanders onto a catwalk suspended over the men's recreational area. With the door at the other end of the catwalk locked, she is forced to fight her way back past the men who are trying to climb up onto the catwalk and grope her, and returns to her room in defeat.Later, Mrs. Venable drops by the hospital to check on the status of Cukrowicz's evaluation. The doctor persuades her to meet Catherine face to face. In the ensuing confrontation, Catherine tries to get her aunt to reveal the true nature of her relationship with Sebastian and the reason why she was left behind and Catherine chosen to take her place as his traveling companion, vaguely hinting that Sebastian used them as "bait" and that they "procured for him". Mrs. Venable responds to these allegations by fainting. Catherine uses this opportunity to slip away again to find another way to escape from the hospital. Catherine finds another catwalk that runs above a rec room filled with women who initially stare at her in silence as she walks overhead. She climbs the railing and leans out precipitously, considering jumping to her death as the women start cackling below, but before she can release her hold, an orderly (David Cameron) comes up behind her, drags her back to her room and sedates her.In a last-ditch effort to help Catherine, Cukrowicz brings her to the Venable estate where he administers a truth serum that will allow her to overcome any resistance to remembering the details of what happened that summer. Before an audience consisting of her aunt, mother and brother, Miss Foxhill (Mavis Villiers), Dr. Hockstader, and Nurse Benson (Patricia Marmont), all of whom have gathered on the patio in the jungle-like garden, Cukrowicz begins questioning Catherine:In a long silent flashback sequence, Catherine recalls how she and Sebastian spent their days on the beach in the Spanish town of Cabeza de Lobo at a posh resort hotel on the beach. On one occasion, he drags her reluctantly into the water, which causes the fabric of her white bathing suit to become transparent. A group of local young men, who had been watching her from the neighboring public beach, start to approach but are intercepted by Sebastian. Catherine gradually realizes that he is using her as bait to attract these local teenage boys in order to proposition them for sex. Since the boys are desperate for money, Sebastian is successful in his efforts; however, he gradually becomes "fed up with the dark ones" and, being "famished for blondes", makes plans to depart for the northern countries of Scandinavia. On one scorching white-hot day, Sebastian and Catherine are having lunch at a local cafe near the beach when they are beset by a team of ragged street boys playing cacophonous music on instruments of scrap metal and begging for money (some of them being the same teen boys he propositioned to earlier). When Sebastian rejects them, they take up pursuit through the streets of the town. Sebastian attempts to flee, but the boys swarm around him at every turn. He is finally cornered among the ruins of a temple located on a hilltop. In the meantime, Catherine has been frantically trying to catch up with Sebastian, but she reaches him only to see him overwhelmed at last by the group of boys. To her horror and revulsion, she realizes that the starving street teens are literally tearing him apart and eating his flesh. She screams for help, to no avail.The film returns to Catherine, who has collapsed upon the ground, sobbing, and then runs outside the house. Mrs. Venable closes Sebastian's book of poems... the pages of which are blank (there were never any poems in the book, for Mrs. Venable clearly made them up as her own deluded way to deny her son's homosexuality to herself). Mrs. Venable then slowly rises from her seat and takes Cukrowicz's arm. Calling him Sebastian, she tells him not to be out in the sun for too long and that they should go inside the boat and inform the captain that they want to leave. Now clearly insane that the truth has come out, Mrs. Venable is led away and Cukrowicz returns to check on Catherine, who has recovered, having learned the truth. They both walk into the house together.
Output: Question: What is Catherine Holly institutionalized for?, Answer: a severe emotional disturbance