Woody Allen has made so many bad movies for so long and with such clockwork diligence that even mildly positive appraisals of his latter-day output seem like wishful thinking. Despite the A-list casts, the new (and often breathtaking) European locations, the impeccable production design — unanticipated leaps beyond his insular upper-Manhattan comfort zone — and the frequent, flirtatious appearance of his current muse, 23-year-old Scarlett Johansson, it’s been hard for ardent fans of those “early, funny movies” with which Mr. Allen established his name to watch a great American resource dwindle into his dotage.

Maybe Mr. Allen has shared this concern. Because something has given him a genuine kick in the rear. Most likely, it’s a pair of Spanish actors, Javier Bardem and Penelope Cruz. Their embodiment of a smoldering carnality in “Vicky Cristina Barcelona,” Mr. Allen’s latest film, could have been a facile cliché, but instead finds a sublime and eloquent comic release. As star-crossed lovers out of some kind of tortured romantic epic, Mr. Bardem and Ms. Cruz are almost too vital, too visceral, for the tweedy, urban neuroticism of Mr. Allen’s films. (After all, the last time most audiences glimpsed Mr. Bardem, he was wielding a lethal bolt pistol as the serial killer in “No Country for Old Men.”)

But that seems to be the point. And besides, Juan Antonio (Mr. Bardem) and Maria Elena (Ms. Cruz) are both abstract painters — as archetypal an occupation for a Woody Allen character as is, say, the somewhat aimless yet thirsty for worldly experience American student on holiday.

That would be Ms. Johansson’s Cristina, who has just arrived in Barcelona with her best friend Vicky (Rebecca Hall). The girls are a perfect contrast. Cristina is the would-be bohemian, fresh off a broken relationship and a failed art project, eager to seize the moment. Vicky is the serious-minded brunette, reluctant wing-woman and graduate student who has come to Spain to research her master’s thesis on “Catalan identity.” She’s also engaged to marry Doug (Chris Messina), the safe-but-dull boyfriend with suburban dreams that money can buy.

When their summer hostess, Judy (Patricia Clarkson), points out the hunky Juan Antonio at an art opening and drops some gossip about his violent relationship with his ex-lover Maria Elena, the intrigue begins. It’s not long before the young women spy Juan Antonio at a restaurant, where the charismatic artist approaches their table with a point-blank invitation: Come away with him in his private plane to visit Oviedo for the weekend, where they will drink wine, take in nature’s beauty, and make love.

Despite Vicky’s emphatic resistance — prepare to be shocked — they go, although not with the anticipated results. Nonetheless, it’s Cristina who finds herself falling for Juan Antonio … as does Vicky, despite her looming marriage. Also carrying a torch, apparently, is the fiery Maria Elena, who moves in with Juan Antonio after the impulsive Cristina has already taken the plunge and become his newest live-in girlfriend. Maria Elena’s failed suicide attempt and psychological disarray have left no other choice. But after some initial sparks fly, something funny happens: Juan Antonio and his women initiate an unlikely ménage à trois. The brilliant but self-destructive Maria Elena finds a balm in Cristina’s presence, and begins to serve as her photographic muse. The young American proves to be the missing catalyst the old lovers needed to smooth their volatile edges. So much for geometry. Much of the film’s pleasure is in watching how the characters play the various angles, flirt with crazy possibilities, and rationalize their choices.

What Mr. Allen sets up is not dissimilar to his usual romantic comedy strategy. There’s a character with a moral dilemma — Ms. Hall’s buttoned-down but dying to burst open Vicky — who secretly wants to abandon her wedding plans and run to Juan Antonio but can’t, and so nervously frets about it all. In many ways, she is a feminine analog to the nebbishy dudes Mr. Allen specialized in when he starred in his own movies. And there’s the free-spirited character, whose more open views on life and love might simply mean she’s an ardent flake, but create a dialogue that expands when Ms. Cruz enters the frame, illustrating the kind of dangerous, anarchic passion that might have inspired André Breton. What’s different is that Mr. Allen has opened up the usual playing field, allowing Mr. Bardem (and, in her fleeting but deliciously explosive moments, Ms. Cruz) to hijack his ultimately hermetic, shrink’s-couch aesthetic and turn it into a passionate romp. If the director was seduced by the sights and sounds of Barcelona, which are ably heightened to a sensual peak by cinematographer Javier Aguirresarobe, and merely sought an excuse to explore his fascination, then so much the better.

Despite an awkward, third-party narration in an academic male voice (belonging to Christopher Evan Welch) that analyzes the characters as if they were test subjects in an anthropology experiment, the film may be the least abstract of Mr. Allen’s more recent efforts, and the least yoked to the filmmaker’s signature affectations. Perhaps, in all its talky inconclusiveness and postcard vistas, “Vicky Cristina Barcelona” is not very different from one of the more trivial Eric Rohmer comedies, all about the eye candy and some vaguely risqué business regarding the rules of attraction. But in its best moments, when Mr. Bardem and Ms. Cruz lay siege to the screen, reveling in their fever-bed chemistry, it’s as if Mr. Allen has stumbled into an alternate universe — one where his movies are actually worth watching again.