Ex-cop Jung-ho (Kim) works as a pimp, and a couple of his escorts have gone missing. He knows something is up even as he sends his best girl Mi-jin (Seo) to the same client, Young-min (Ha). And sure enough, the lonely young man immediately starts trying to kill her, as he has clearly done many times before. Beside himself with worry, Jung-ho manages to track down the killer, but his anger, police incompetence and a political scandal create a mind-boggling series of obstacles to locking up the murderer and reuniting Mi-jin with her 7-year-old daughter.

Filmmaker Na infuses this film with a frantic pace that grabs us right at the start and lever lets us go. The title refers to Jung-ho's relentless pursuit of the slippery Young-min, trying to rescue Mi-jin from certain death while protecting her daughter and attempting to get the police to realise what's actually going on. It's a mind-boggling juggling act, and the film's writing, direction and editing keep all the balls in the air brilliantly, building almost unbearable levels of suspense along with moments that are powerfully moving.

Kim is superb in the antihero role, a shadowy character with a vicious temper; his former colleagues (including Jung and Park) still trust him, even as they see him as a dangerous loose cannon. Everyone else thinks he's the actual villain, and that his brutal treatment of Young-min is the real crime, even after Young-min confesses to the murders. And we know something no one else knows: not only is the clock ticking for Mi-jin but, despite his boyish looks and disarming manner, Young-min is a true monster.

In this sense, the film manages the rare feat of breathing new life into the serial killer genre with gritty realism and an almost overwhelming life-or-death struggle. This is expert filmmaking at every level, continually adding engaging subtext that touches on family pressures, blind self-interest and warped justice. So it's hardly surprising that Hollywood has already signed on for a remake, although it's highly unlikely that they'll stick to this film's wrenching climax.

Over his school break teenager Rille (Jerry Johansson) is teaching ping-pong, which he calls "the last remaining egalitarian sport". His favourite opponent is his polar-extreme little brother Erik (Hampus Johansson)--Rille is tall, dark and big; Erik is short, blond and wiry. And there are other clues that convince Rille that he's actually the son of Gunnar (Nilsson), the boyfriend of their mother (Nurmi), rather than the adventurer (Staykov) he and Erik call dad. But unexpected revelations are in store. And Rille's potential girlfriend (Stewén) has some eye-popping surprises of her own.

Filmmaker Jonsson takes a dry and often very funny approach in the early scenes, combining witty camerawork with low-key Napoleon Dynamite-style humour. But besides being a typical lonely, fat kid, Rille is haunted by questions about his identity that are pretty severe for a teen to bear, especially when he sees his closest confidant (his little brother) slipping away from him.

These character details make the film thoroughly engaging. And the plot is refreshingly unpredictable, never taking the likely route through a situation. That said, there are several clunky narrative devices that signpost events to come, including that old chestnut: show us a hidden gun and we know someone will come back to get it later. It's also a rather severe slide from goofy comedy to heavy melodrama to wrenching thriller. Although the cast members maintain their characterisations perfectly through it all.

Visually, the film has a quirky, surreal style, with characters who continually do hilarious things and yet also swerve into careless cruelty. The film is shot and edited with an attention to clever sight gags and, as it progresses, this approach is used inventively to heighten the drama and tension. And best of all is how the story examines the point in several characters' lives where they will need to shift gears and take a new path, whether they want to or not.

Pierre (Duris) is an ex-dancer in need of a heart transplant, and when his sister Elise (Binoche) finds out, she drops everything and moves in to both take care of him and cheer him up. Over the following months, they cross paths with a variety of people: a market seller (Dupontel) who still has feelings for his ex-wife (Ferrier); a professor (Luchini) whose brother (Cluzet) doesn't get him and whose student (Laurent) is a bit frightened by him; and an obsessive, mildly racist baker (Viard) who reluctantly hires a North African assistant (Ouazani).

Klapisch puts this all together in a slightly tidy way, making sure to capture a spectrum of economic and ethnic characters who interlink meaningfully, with carefully woven stories that overflow with comedy, tragedy and the small adventures of everyday life. Each character makes a few self-discoveries and connects unexpectedly with someone else, which of course gives the talented cast a chance to shine in their roles.

Duris is especially effective, managing to hold our attention even when he mopes, then delivering the pay-off in a superb party scene in which he tries to regain his former spark. His scenes with Binoche are lively and enjoyable. All of the romantic plotlines are remarkably sparky. And the other standouts in the sprawling ensemble include Luchini, who has a series of hilariously embarrassing encounters and yet maintains an engaging dignity, and the marvellous Viard in a glorified cameo that speaks volumes.

Essentially, the only thing that ties these characters together is the city in which they live or, in the case of one plot strand set in Cameroon, the city they long to reach. And while the film ultimately feels rather lightweight, there are several terrific moments along the way: tiny acts of kindness and carelessness, private motivations, sex that's startlingly nervous for a French film, and scenes that are shocking, sad and sweet. Yes, it does wander all over the place, but the film really does capture the tone of life in the City of Lights. And it often hits cords that resonate much further afield.

In Quiapo, a district of Manila, a group of people are confronted with daily struggles, on constant watch for the raiding policemen, who don't care if their target is the young father of a screaming baby, a sickly middle-aged man or a schoolboy. There aren't many legitimate jobs in this place, so in order to pay for things like food and medical care, residents resort to pick-pocketing, drug dealing and selling bootleg videos. Meanwhile, politicians court votes by bailing guys out of jail, playing on the deep-seated Catholicism or handing out cold, hard cash.

Mendoza's shaky camera follows the large cast of characters through narrow passageways, up and down stairs and out into the streets, drifting from person to person to capture a wide variety of stories. It's virtually impossible to keep everyone straight or follow any one plotline, as the narrative leaps ahead, skips around and presents each person with new wrinkles in their life. This approach is often quite thrilling; even if we can't engage with a character, we are gripped by the raw energy and fiery interaction.

The most admirable achievement is the overwhelming sense of energy in this grim place. Even though almost everyone is up to something illegal, they have a basic set of (relative) morals. Within this, the men are all brutally macho, offering no help or respect to their women. And one thief angrily confronts his victim when he discovers that the necklace he stole was a fake: "You wasted my time!"

The lean, sweaty, muscled cast members bounce off each other with earthy vigour. And the snappy camerawork and vivid editing constantly add irony and wit. For example, it's clear that casting a vote is about the same as playing the lottery: both offer promise for the future and they're equally unlikely to pay off. In the end, the lack of a plot and the general hopelessness wear us down. But the film never outstays its welcome, and the characters never give up on life.