In Before Sunrise, the 1995 film about two young travelers who spend a night together in Vienna, the American Jesse (Ethan Hawke) says he views himself as a perpetual 13-year-old boy. Celine (Julie Delpy), the Sorbonne student he's met on the train, responds that she sees herself as an old woman, forever pretending to be young.

Eighteen years later, with the characters now in their early 40s, those self-perceptions seem, if anything, to have deepened. Jesse still has the same crooked smile and tendency to crack wise whenever conversation turns serious, and the more practical Celine grows frustrated with his evasions and self-absorption. For those coming late to Richard Linklater's now-epic cinematic romance, a recap: After the dreamy, witty gabfest of Before Sunrise, the two didn't meet again for nine years, until she tracked him down at a book reading in Paris. That reunion was the subject of 2004's luminous Before Sunset. And now, again nine years later, Jesse and Celine are back in the nearly perfect Before Midnight: coupled, living in Paris, raising flaxen-haired twin moppets bilingually.

Before the romantics rejoice, know that while Jesse and Celine still have spark, their nervous, youthful energy has been supplanted by something harder and sharper, as they navigate the challenges of maintaining a relationship. In Before Midnight, they've come to the end of a blissful summer in Greece. Early on, Linklater provides one of the uninterrupted takes that showcase the brilliant rhythms of his unobtrusive filmmaking. The take is nearly 15 minutes, shot in a car, as Jesse and Celine traverse from a discussion of parenting style to playful flirting ("I've got a Trojan in my billfold and a rocket in my pocket," Hawke croons) to heated talk about the future. Jesse's ex-wife lives in Chicago; Jesse wants to be closer to his teenage son; Celine thinks Jesse is asking her to relocate to the Windy City.

That debate is bound to come up later, and does it ever, at the hotel where Jesse and Celine are supposed to be having an amorous evening away from their daughters. That argument—a remarkable half-hour that should go down in cinematic history—is funny, painful and thoroughly astounding. Hawke and Delpy inhabit their roles so completely, and their characters are so good at manipulating conversation, that I found my loyalties zinging back and forth as if in a high-speed, particularly vicious game of pingpong. Not, of course, that I wanted one partner to win—I just wanted it to stop. Or, maybe, I didn't. Critic's Grade: A 

SEE IT: Before Midnight is rated R. It opens Friday at Fox Tower, Eastport, Bridgeport, Clackamas, Lloyd Mall.