A lot of movies are important and admired—the National Film Registry list is a testament to just that—but only a handful are truly beloved. At the mention of their titles, the eyes get all moist and faraway and the mind’s projector unspools favorite scenes, frame for frame, the dialogue verbatim. We admire the cinema of Alfred Hitchcock and Stanley Kubrick. We get mushy over The Wizard of Oz, Shane, and E.T.

To Kill A Mockingbird, which celebrates its fiftieth anniversary this year, belongs in that rarified realm. Based on Harper Lee’s equally beloved novel, one of the few works of American literature high school students will read without a gun pointed to their heads, the Alan J. Pakula-produced, Robert Mulligan-directed, and Horton Foote-scripted adaptation is the perfect companion piece to the book, so in tune with the sensibility of Lee’s dappled prose, so evocative of the visionary gleam of childhood, that it shuts down all those dreary book-or-movie arguments: Atticus Finch is Gregory Peck is Atticus Finch.

Courtroom drama, crime thriller, family melodrama, horror film, and female bildingsroman, the tale is a rite-of-passage mood piece seen through the six-year-old eyes of the tomboy adventurer Scout (played by nine-year-old non-pro Mary Badham, her pixie face framed by a helmet of black hair). Under the spell of Elmer Bernstein’s dream-weaving score and Stephen Frankfurt’s found-object title sequence, we immediately plunge into the age of not-so-innocence: a little girl’s voice hums softly as she fiddles through the treasures of a cigar box—crayons, marbles, old coins. Scout has a protective older brother Jem (Phillip Alford) and a mother-surrogate housekeeper Calpurnia (Estelle Evans), but her sun rises and sets on her lanky, Lincolnesque father, Atticus, whose very name bespeaks the classical virtues of a noble man standing for republican principles against the passions of the mob. If the father is absent, the boy must seek a substitute; if the mother is absent, the girl is happy to have Dad all to herself.

The setting is Alabama in the early 1930s, ground zero for the Jim Crow South, but of course neither book nor movie is a period piece: the real setting is America in the early 1960s, during the full bloom of the New Frontier and the forward march of the civil rights movement. The trial of a black man accused of raping a white woman serves as the stage for the children’s own freedom summer, a lesson acted out in a separate but unequal courtroom whose seating arrangement—black folk in the balcony, white folk on the main floor—mirrors the position of the races in segregated theaters south of the Mason-Dixon line. Yet even Atticus is trapped by history: in keeping with local custom, Calpurnia rides in the back of his car, not up front in the passenger seat.

Jim Crow being no fairy tale, the imagination of the children fixes on the boogie man who lives down the street, the mysterious Boo Radley (Robert Duvall, pale and white-haired in his big screen debut). A spectral hobgoblin who becomes a guardian angel, he gives the film its title and twist. Scout, her mouth creasing into a smile of recognition, exhales a greeting that is also an epiphany: “Hey, Boo.”

Like all the best uses of enchantment from the Brothers Grimm to Walt Disney, To Kill a Mockingbird has a scary underside and a stiff backbone. A key scene occurs when a rabid dog wanders into the neighborhood. As Jem and Scout watch wide-eyed, the sheriff hands his rifle over to Atticus for a demonstration of the frontier skill of marksmanship. Atticus is kind, gentle, and moral, but he knows his way around more than law books. The liberalism he embodies is in the JFK mold, vigorous and forceful, not given to flinch at violence or freeze up with endless, anguishing self-examination. When a rabid dog comes into your neighborhood, you don’t try to reason with dog, you don’t consider that dogs have been victims of human oppression for untold millennia, and you don’t consider a more ethical treatment of the animal. When a rabid dog wanders into your neighborhood and threatens your children, you shoot the dog.