A movie must stand on it own legs. If it must be explained by its filmmakers or propped up by our vivid, fill-in-the-missing-parts memories of a book, play or previous film it is based on, then somebody has fallen down on the job.

That’s the case with “My Golden Days,” director Arnaud Desplechin’s 20-years-later prequel to “My Sex Life… or How I Got Into an Argument.”

“Golden Days” once again features Desplechin’s muse, Mathieu Amalric (“Quantum of Solace”, “The Diving Bell and the Butterfly”) as anthropologist Paul Dedalus, reminiscing over a couple of specific memories of his youth. The film’s French title is “Trois souvenirs de ma jeunesse,” or “Three souvenirs/memories of my Youth.”

It’s a vivid recreation of a time (the ’80s), a place and an intense, physical letter-strewn love affair of youth. But as a stand-alone film it flirts with utter incoherence.

Start with Paul’s last name. Dedelus, aka Daedalus, like the Greek craftsman who made wings for his son Icarus? This is significant, how? He’s crafting his own story? OK.

Then there’s the structure. Paul leaves behind his Russian girlfriend to return to France for a government job. The film is basically a flashback contained (sort of) within a French interrogation he undergoes thanks to a passport indiscretion long ago.

Using multiple, almost randomly selected narrators, “Golden Days” traipses back to Paul’s angry childhood, his “mad” then dead mother, his abusive, broken father (Olivier Rabourdin) and a teenage class trip to the Soviet Union.

The film breaks away from that Soviet thread as Paul (and other narrators) are sidetracked by the great love of his young life, the sultry Esther (Lou Roy-Lecollinet).

The effect is more chronological than cohesive, and while we follow Young Paul (Quentin Dolmaire) through both story threads, their connection is tenuous, even at the coda.

By which time Desplechin has long since abandoned the flashback, moved forward in time to a point where Paul plainly is clinging to the bitter aftertaste of the end of an affair.

The three stories from the past show the bond between Paul and his siblings, Ivan and Delphine and the risk-taking that their shared childhoods drove them to in adolescence.

Ivan dives into pot and flirts with gangsterism. Paul? He joins a Jewish friend in a risky, escape-from-their-tour-group adventure as couriers for Soviet era (@1980) “refuseniks,” Jews who dissented against the powers of the oppressive police state. Paul came home with a black eye, a story to tell and, it turns out, a future passport issue thanks to his naivete/heroism.

The meat of the movie is the young love/first love affair with Esther, an overripe, Bardot-pouty siren who is awfully popular with the boys.

“My eyes devour you,” he confesses (in French, with English subtitles), sure she’s out of his league.

“I always have that effect,” she smirks in agreement, in between drags on her sexy French cigarette.

They’re sophisticates. He’s more confident than he lets on, sweet-talking a famous Paris anthropologist (Eve doe-Bruce) into taking him on as a student. Esther is abandoning her many other lovers and pining away for Paul in their provincial hometown. Roy-Lecollinet makes of feel how breathless Paul makes her feel.

This love affair, aching and sexual, is the beating heart of the movie and makes one wish Desplechin had given full voice to his Francois Truffaut worship and made this his “400 Blows.” The Soviet story is intriguing, but underdeveloped. The rage of childhood feels tacked on.

Still, “My Golden Days” is inviting enough to make you curious about its precursor. My memories of “My Sex Life” are thin, at best. But binge-watching them both, back to back on some future wintry Netflix/Amazon streaming date may add sense to the seeming randomness of Desplechin’s wanderings. But as a stand-alone film, “Golden Days” feels leaden.

MPAA Rating:R for some strong sexual content, graphic nudity, and language

Cast: Mathieu Amalric, Quentin Dolmaire, Lou Roy-Lecollinet , Olivier Rabourdin, Eve Doe-Bruce
Credits: Directed by Arnaud Desplechin, script by Arnaud Desplechin and  Julie Peyr. A Magnolia release.

Running time: 2:03