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."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 â even though he only wrote a single poem each year during the summer months and never published his work â and recounts her own previous vacations with him. Cukrowicz agrees to visit Catherine and begin his evaluation. Catherine has been confined to a private women's mental institution since returning from Europe several months earlier. When Cukrowicz interviews her, she struggles to recall the specific events that led to Sebastian's death and her subsequent breakdown, but expresses a sincere 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, Grace (Mercedes McCambridge), and brother, George (Gary Raymond), pay her a visit there and reveal that Sebastian has left them a considerable sum of money. 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 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. Using this opportunity to slip away, Catherine finds another catwalk that runs above a room filled with women. She climbs the railing and leans out precipitously, considering the jump, 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 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. She recalls how she and Sebastian spent their days on the beach in the Spanish town of Cabeza de Lobo. On one occasion, he drags her reluctantly into the water, causing the fabric of her white bathing suit to become transparent. A group of young men who had been watching her from the neighboring public beach start to approach but are intercepted by Sebastian. Catherine comes to realize that he is using her to attract these 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 blonds," makes plans to depart for the northern countries. One scorching white-hot day, Sebastian and Catherine are beset by a team of boys begging for money. 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 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 by the boys. To her horror and revulsion, they begin to tear him apart and eat his flesh. She screams for help, to no avail.At this point in telling her astonishing account of Sebastian's demise, Catherine has collapsed upon the ground, sobbing. Her mind undone by the shock of hearing Catherine's tale, Mrs. Venable closes Sebastian's last book of poems, the pages of which are blank, 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. Mrs. Venable is led away and Cukrowicz returns to check on Catherine, who has recovered. They both walk into the house together.
Output: Question: Who plays Grace?, Answer: Mercedes McCambridge