It occurred to me while watching “Bernie,” the totally engrossing Jack Black dark comedy, that Richard Linklater may be one of the most underrated living writer/directors. The auteur who arrived with slacker hits like “Slacker” and “Dazed and Confused” now solidifies my sentiment on this issue with “Before Midnight.”

For those who haven’t seen the previous Ethan Hawke-Julie Delpy talkfests, “Before Sunrise” and “Before Sunset,” you'd do well to check out those films. They take place nine years apart, the first introducing the American Jesse to a French woman, Celine, via a chance encounter on a train. The second finds them reunited in Paris, where Jesse is touring with his novel about the events of the first film.

“Before Midnight” finds the couple nine years on, living in Europe with two twin daughters. To go into the specific plot machinations would cheapen all this a bit, so suffice it to say that all three movies revolve around long set-piece conversations that feel eerily naturalistic, as if Linklater is filming two good-looking loquacious people for a reality show.

(True movie nerds will recall that Jesse and Celine also featured into a scene from Linklater’s animated film “Waking Life,” although they are never identified by name.)

What impresses so much about “Before Midnight” is the way we can see Jesse and Celine’s younger selves beneath their aging faces, the way their banter calls to mind all the conversations from the previous films, yet now each interaction is tinged with the resentment and bitterness that accumulate over the course of any long-term relationship. The backstory gets filled in slowly over the course of a day, and through all these circular, repetitive arguments the scope of their complicated pasts and shared present becomes revealed.

Where “Before Sunrise” was the kind of winsome fantasy just about every young American guy traveling abroad entertains (I first saw it in a film class in Florence, Italy, which basically set the tone for how I behaved that entire trip), “Before Sunset” served as a heart-heavy assessment of youthful decisions. Where did each of these two people go wrong? What mistakes were made and what could have been done differently? “Before Midnight” catapults the series into familiar yet darker territory. Jesse’s novels detail his grand romantic encounter, but he then changed his life for the girl he met on the train, and now here’s what the epilogue to that decision looks like. Turns out it looks like a fascinating and candid movie about the ways in which love can be both exhausting and entrenched.

In fact, “Before Midnight” now takes the first two films to another level. Now that Linklater, Hawke, and Delpy (the two stars co-wrote as well) have revealed the full scope of their vision, it stands as one of the most impressive cinematic experiments of our time. An epic told through nothing more than following around two attractive, over-educated wiseasses for three different days of their lives.

Perhaps the characters feel familiar because now fans have had two decades to recommend, re-watch, and admire Jesse and Celine for all their humor, flaws, and frustrations. Jesse is, for the most part, every writer cliché ever (although I can attest, male writers tend to live up to way too much of that stuff), and Celine is basically Julie Delpy, the actress, who instead became an environmentalist (Delpy, the director, has made two not-as-good films in the exact same mode of the “Before” series: “2 Days in Paris” and “2 Days in New York”).

Yet the collaboration between Linklater and the two actors really does give this third film its own vitality and verisimilitude that should move Linklater’s name up the list of his generation’s most impressive directors.