There is a third rail for many film-makers, the alluring danger of quirk. Quirk is a somewhat indefinable thing but, to paraphrase supreme court justice Potter Stewart, we know it when we see it. There are some, however, who know how to harness its powers, and six years after the festival debut of Beginners, designer, music video director and guy-with-cool-associates Mike Mills has stepped back behind the camera to one-up himself. 20th Century Women is a rushing river of gorgeous moments, a full-frontal assault of poetic observation and craftily constructed vignettes. By being about nothing specific (is there even an elevator pitch here?) it manages to be about everything, a coming-of-age tale about a kid that’s “different” but not too different. Moreover, it proves that Mills is no dilettante, he has developed a very specific style that is, above all the poignancy, deliciously watchable.

20th Century Women works as a diptych to Beginners, which won Christopher Plummer an Oscar for his portrayal of a 75-year-old widower and father living his last years as a gay man. It was taken from Mills’s own family history and, after a quick glance at Wikipedia, one can see how Annette Bening’s character Dorothea is based on Mills’s mother. (Were one to lay odds, one could also feel confident that she’ll come away next year with her fifth Oscar nomination, and maybe her first win.) She is a free-thinking and independent woman, devoted to raising her son Jamie (Lucas Jade Zumann) as a moral individual, but strangely determined not to take action against her unhappiness. (In this version, the dad is out of the picture entirely, only calling on birthdays.) Dorothea takes in boarders in her enormous southern California house, which is under continuous renovation.

Yeah, it’s that sort of symbolism-for-dummies that a lesser film-maker wouldn’t be able to handle, but Mills knows how to massage it into the background. He’s also quite adept at weaving music and fashion of the era (the film is set in 1979) so that it is authentic but not overbearing. This is a movie in which a fifty-ish woman who loves Glenn Miller and Louis Armstrong takes a lesson in Black Flag v Talking Heads and, somehow, it isn’t just an excuse for a director to profess love for his influences. By the time we hit this scene we understand Dorothea’s need to try to understand the kids of today, and we’re right there with her as she half-enjoys, half-shrugs at the current styles.

Dorothea’s style is more of the silk pyjama, ubiquitous cigarette, tuxedo cat on her lap and crooked smile variety as she gives motherly advice to the other two women of the title: Abbey (Greta Gerwig), a would-be photographer with a New Wave haircut, and Julie (Elle Fanning) halfway between worldly and bewildered, and the object of her son Jamie’s affection. Her home is something of a base for everyone, and that includes the lost mechanic William (Billy Crudup), a good guy, but also exhibit A in how to be a distant and somewhat useless man. How each of these characters ended up in Dorothea’s orbit is teased out through flashbacks, voiceover, use of pop culture images and readings from various texts. (The words of Judy Blume, M Scott Peck, Jimmy Carter and the essays contained in Sisterhood is Powerful: An Anthology of Writings From the Women’s Liberation Movement all make an appearance, as do clips from Godfrey Reggio’s Koyaanisqatsi.)

Inasmuch as there is a traditional plot in 20th Century Women it comes when Dorothea realizes Jamie, now 15, needs more than just a mom to raise him, so she recruits Abbey and Julie to help out. She’ll soon realize this maybe isn’t such a hot idea, as Abbey, a cancer survivor, is still figuring stuff out herself, and Julie (still only 17) has put Jamie in the most epic of friend-zones, despite sleeping in his bed each night. By the end, of course, all will realize that this was the best idea ever, as this is, more than anything, a film about nostalgia, and how memory can be used to make everything seem perfect.

Mills’s technique is rich with editing, music and (dare I say it?) quirky transitions, but, as with Beginners, the performances are what linger. All are terrific, and that includes relative newcomer Lucas Jade Zumann, but this is Bening’s show. She’s given some marvelous zingers (“wondering if you are happy is just a shortcut to being depressed” and, regarding her love of cigarettes, “when I started they weren’t bad for you, they were just stylish”), but it’s the type of role where merely watching her listen is a revelation. She’s part-brash, part-terrified, wanting so much to be a strong mother, but worried about losing her son to the forces of time. I can’t remember the last time watching a woman walk into a kitchen and just stand there got a laugh from an audience. Importantly, it wasn’t a laugh from a joke, it was a laugh of understanding. For all of Mills’s cinematic tricks, he’s emerging as a great realist film-maker.