First-time director Alejandro Gonzalez Inarritu diplays an impressive range of moods in "Amores Perros."

The film opens in the middle of a kinetic, pulse-quickening, panic-driven car chase/gunfight through the congested streets of Mexico City. It features disturbingly realistic underground dog fights from the city's extremely ugly underbelly. Yet there is tenderness and emotionally authentic sorrow in the stories that go along with these brusque and disturbing scenes.

Even more impressive is Inarritu's cinema verite sense of over-the-shoulder storytelling and his ability to seamlessly weave together a "Pulp Fiction"-like reciprocal timeline tapestry of three harsh yet appealing tales, all of which evolve from the violent crash that ends that opening chase.

At fault in the crash is teenage Octavio (Gael Garcia Bernal), a small-time player on the brutally portrayed dog-fighting scene. He was trying to get his beloved mastiff -- bleeding from a gunshot wound -- to a hospital after winning a fight that enraged a gang-banging rival.

After opening with the chase and crash -- shot in a cringingly realistic way that's more "Cops" than "Ronin" -- Inarritu jumps backward to unspool the story of compassionate Octavio and his fervid desire to romance and rescue Susana (Vanessa Bauche), the abused young wife of his bullying petty criminal brother. Bernal solicits a strong sense of sympathy, despite Octavio's often foolish choices, as he desperately seeks out ways for the two of them (and Susana's baby) to flee their shared tenement household -- even though Susana isn't all that sure she wants to leave with him. Eventually he begins fighting his brother's dog in high-stakes, to-the-death brawls to raise money.

At the same time, the film follows an adulterous husband named Daniel (Alvaro Guerrero) and Valeria (Goya Toledo), his fashion model mistress who is horribly mauled in the accident when Octavio broadsides her Mercedes at high speed. Having just left his wife and set up an expensive new love nest, Daniel's life is thrown into turmoil by the aftermath of the accident and its physically and psychologically paralizing effect on his beautiful lover. She now finds solice only in the companionship of her precious little lap dog, who miraculously survived the crash unscathed.

The omnipresence of pet pooches (and -- as a metaphor for the devaluation of human life -- dead and bloody fighting pooches) is another element that ties the episodes together in this cunning, cut-rate cinematic saga. (Even the title translates losely as "Love's a Bitch.")

Shot in sharply colorful, digi-gritty digital video and so nimbly edited that even when a character disappears for 20 minutes the audience never loses track of him, "Amores Perros" successfully navigates overlaping and intersecting volumes of engrossing story without a slip.

At times it feels annoyingly vague, but you soon learn to trust Inarritu and go with the flow. One of these times is the introduction of the third story, which seems to come out of nowhere and be utterly unconnected until it suddenly steers toward a graying, enigmatic, and seemingly unstable homeless man (Emilio Echevarria). He has been hovering around the accident scene each time the film returns to the crash in between episodes (an increasingly intense score and more abbreviated editing making every revisit different).

The old man is, in fact, a mentally volatile former revolutionary and will-work-for-food hit man who lives in squalor with a pack of stray dogs and quietly stalks his adult daughter whom he'd abandoned in her childhood. Echevarria's performance in this role is the film's most intense. Even as he steals money from one of the crashed cars or toys with the mind of a mark he's kidnapped instead of killed (for reasons not yet known), he's tragically sympathetic and at the same time shows a bit of genial yet nefarious charm.

The film is also a bit frustrating at times, because some other characters (namely Octavio and Susana) have habitually bad judgement that can only beget more trouble. But again, the performances of Bernal and Bauche rescue these characters from our (or at least my) exasperation.

But none of its minor shortcomings can take away from the exceptional talent displayed both in front of and behind the camera in this inventively restless and relentlessly potent rumination on coincidence, consequence, fate, love and seizing opportunity in whatever form it comes knocking.