Her name is Mabel Longhetti. She lives in Los Angeles in the 1970s and wears housedresses with big flowers on them. She's in her 40s, beautiful, a homemaker, a smoker, a tornado of energy. And the moment she runs into the frame—hurrying the kids into grandma's car to get ready for a night-without-the-kids with her husband—the movie shatters open, pops to life, pulls your eyes in. Mabel is played by Gena Rowlands, the real-life wife of John Cassavetes, who wrote and directed A Woman Under the Influence (SIFF is showing a restored print this weekend), and you can tell that he had access to her in ways usually unavailable to directors. This lady they created together is a freakishly vibrant mammal.

Rowlands's costar is Peter Falk, who felt strongly enough about Cassavetes's screenplay that he asked to play Mabel's husband and invested $500,000 of his own money in the film (the total budget was around $800,000). It was shot in 10-minute takes by a somewhat untrained crew instructed to let the actors do whatever they were going to do and try to capture it, documentary style, granting plenty of room for spontaneity. Adding to the suspense, according to interviews, Rowlands and Falk were deprived of information about what the other was going to do. The result is a crackling animalism. It's like two beasts walked onto the set, devoured the actors, and took over.

She's more of an animal than he is. On the one hand, she keeps a tidy house, her kids are well-behaved, and she's fully capable of whipping up spaghetti for a dozen men when her husband, Nick, comes home from work unannounced with his hungry coworkers in hard hats. On the other hand, she's really super weird—physiological spasms, gesturing at nothing, talking like a baby, scrunching her nose like a rabbit, dancing on the furniture, repeating adult conversations in a singsong voice, etc. After sending the kids off, an all-night crisis keeps Nick at work, so she wanders around the house smoking, then out into the street, then into a bar, where she tugs at the nape of a stranger's neck and starts talking to him like they're old friends and goes home with him and, when they wake up, insists that he is Nick. The man does not know who Nick is. "I'm not in the mood for games, Nick," she says determinedly. "Nick Longhetti," she says, pointing to him. "Mabel Longhetti," she says, pointing to herself.

Since the movie was released in 1974 and since Mabel has no purpose other than taking care of the household, it seems coded in feminist question marks: Is she truly crazy, or is she just rebelling against society's rules? With nothing else to occupy her time, isn't it plausible that a woman in the prime of her life might naturally fall into a vortex of formless neuroses and start giving them form?

That spaghetti meal is one of the most awkward, fascinating dining-room scenes in American cinema. When one of the workmen starts singing opera, Mabel goes over to him and puts her face bizarrely close to his singing-at-full-volume mouth, trying to look down his throat, and then she tries to get another of the men to dance, and Nick, embarrassed at her behavior, screams, "Sit your ass down!" Later, she insists she was simply trying not to be a stiff, not to be a square. The subtext of the scene—men can do whatever they want (spontaneously start singing opera) and no one finds it crazy—only dawns on you later, because of your focus on the surfaces: the angles, the acting, the dialogue.

Ultimately, it's a movie about character, allergic to political messages and the vectors of social theory. Mabel is such an original creature that the idea of her standing in for womankind is absurd. Is she psychotic? Eccentric? On to something? Rowlands's performance incinerates anything remotely close to an answer. Even the critic Pauline Kael, who disliked Cassavetes's films, finding them murky and actorly, admired Rowlands's range this time out: "Mabel fragments before our eyes: a three-ring circus might be taking place in her face. Rowlands' performance is enough for half a dozen tours de force, a whole row of Oscars—it's exhausting."

Falk's performance is awesome, too. He is embarrassed by her and in love with her simultaneously. Halfway into the movie, he decides to commit her to a mental hospital, then (with a few marvelously complex facial expressions while watching her lose her shit) his animal love for her overwhelms him and he changes his mind. He turns on the doctor who's arrived. Nick's fire-breathing mother overrules her son: "This woman has to go! This woman can't stay in this house anymore!"

Nick's mother is a minor character, but crucial, and the actress playing her is so good it's surprising to discover that she's John Cassavetes's mom. (She only did three movies, all by him.) Some of the kids are Cassaveteses, too. A Woman Under the Influence is a masterpiece of filmmaking, marvelous in new ways every time you watch it, and proof that you can make a fascinating, stylish, complicated movie with no studio backing, no distributor (Cassavetes distributed it himself, by calling up independent movie theaters and college campuses), and a cast and crew of friends. They were a family, a unit, a brood. This movie is about a hundred different kinds of love.