Regal and nutty as Lady MacBeth, Violet Venable (Katherine Hepburn) is in mourning over last summer’s sudden death of her son, Sebastian, a poet who spent nine months pondering and three months — the summer — producing a single, vanity-press poem whilst on some posh holiday with his widowed mother.

“People didn’t speak of ‘Sebastian and his mother’ or ‘Mrs. Venable and her son,’” Venable says, wrapping a crisp white shawl over her shoulders. “They said, ‘Sebastian and Violet.’ ‘Violet and Sebastian are at the Lido. They’re at the Ritz.’ And every appearance, every time we appeared, attention was centered on us. Everyone else eclipsed … Each day, we would carve each day like a piece of sculpture.”

Until last summer. Venable had a stroke, and Sebastian decided his bombshell cousin Catherine (Elizabeth Taylor) should accompany him. At the Mediterranean town of Cabeza de Lobo (“the head of the wolf,” in Spanish) he has a heart attack and falls to the ground, dead. A stunned Catherine is institutionalized by her aunt.

We hear this story over the shoulder of Dr. Cukrowicz (Montgomery Clift), a young brain surgeon at a shabby state mental hospital back in a time (1937) in which his work would have only been lobotomies. Even Cukrowicz is leery of his work, especially when the disgustingly rich Venable approaches his hospital, promising monsoons of cash if the doctor will just slip his 10-blade into Catherine’s gray matter to cease her “dreadful, obscene babbling.”

This arouses his suspicion and, creepily (except that lobotomies didn’t stop being practiced for more than 10 years after this movie was made), no one else’s.

So who was the deceased, Sebastian? A pampered boy who curated a jungle in his backyard — complete with Venus fly traps — sat in a centuries-old jester’s chair and drank frozen daquiris with his mother every evening at 5. And who was his cousin the survivor, Catherine? A shell-shocked girl who had been raped that summer by a purported gentleman who pretended to be chaperoning her home from the Mardi Gras ball. Who, despite her trauma, made her way back to the ball to assault her attacker in public, to beat on his face in front of high society. Who would not forget how her cousin treated the natives in Europe, how he had tired of the Mediterranean and booked their next leg to Scandinavia, because he was “famished for the light ones.”

“You’ve got to cut this hideous story out of her brain!” Venable shrieks.

Adapted by Gore Vidal from a play by the unmatched Tennessee Williams (whose older sister underwent a lobotomy), “Suddenly, Last Summer” is among the finest films ever made, as shocking and brutal as it is beautiful and fresh. It is a delicate skewer of a movie. Its surgery aims not to cut out something to make things easier, but rather to find the things that make it difficult — how a mother will sell out a daughter for money, how an aunt will kill a brain to keep herself wrapped in delusion, how a passive, poetic son will humiliate his female cousin to lure hungry, sexy foreign boys to his side.

“Nature isn’t created in the image of man’s compassion,” Cukrowicz tells Venable early on, when she relates her horror at seeing raptors eat just-hatched baby sea turtles in the Galapagos Islands. But Venable protests too much at the horror, and Cukrowicz leaves something out of his comment. Man’s compassion is fickle. The raptors are just hungry. Venable can’t sympathize with a powerful beast forced to devour something adorable. She would kill to assuage her own discomfort — and that’s far more beastly.