Ronin is the Japanese word used for Samurai without a master. In this case, the Ronin are outcast specialists of every kind, whose services are available to everyone - for money. Dierdre (undoubtedly from Ireland) hires several Ronin to form a team in order to retrieve an important suitcase from a man who is about to sell it to the Russians. After the mission has been completed successfully, the suitcase immediately gets switched by a member of the team who seems to work into his own pocket. The complex net of everyone tricking everyone begins to surface slowly, and deadly...
A woman assembles a team of professional killers from all over the world to get a hold on a certain case with some mysterious content. The case is in the hands of some ex-KGB spies and there are many people and organizations that will do anything to get it
A freelancing former U.S. Intelligence Agent tries to track down a mysterious package that is wanted by the Irish and the Russians.
- In a Montmartre, Paris café, an Irish woman named Deirdre (Natascha McElhone) meets five men, taking them to a warehouse and briefing them on a mission. The men, Spence (Sean Bean), Larry (Skipp Sudduth), Gregor (Stellan Skarsgård), Vincent (Jean Reno) and Sam (Robert De Niro), are all former Special Forces soldiers or intelligence operatives now working as mercenaries. The team are planning to attack a heavily-armed convoy and steal a suitcase, its contents unknown (a MacGuffin). Following the briefing, the team begins assembling their equipment. Deirdre meets with her handler Seamus (Jonathan Pryce), who reveals that Russian gangsters are bidding for the case and that the team must act quickly to intercept it.
The team goes over the plan with Deirdre. Vincent will provide the team with any technology they need, including vehicles with modified engines. Spence is a weapons expert who sets up an exchange for the team. He, Sam, Vincent and Larry meet Spence's contacts under the Pont Alexandre III (Bridge of Alexander III) on the Seine. When Spence talks to the dealers, he's dismayed to find that they brought only half the weaponry he'd ordered. The other half is allegedly in another car on the other side of the bridge. Sam immediately smells a trap but agrees to accompany Spence for protection. As they approach the dealers' shady boss, a fat man in an overcoat, Sam sees a sniper hiding in the rafting of the bridge and shoots him. The rest of the dealers open fire while Spence, Vincent and Sam return it. Larry picks them up after securing the cases and the team roars off at high speed. When they determine they're not being pursued, they pull off the street, allowing Spence to exit the car and vomit. Vincent asks Sam why he took the job and Sam tells him he needs the money. He and Vincent share a knowing smile.
Later at the warehouse, Spence is exposed as a fraud when he offers an incompetent plan of attack and is summarily released from the team. Deirdre informs them that they'll capture the case near Nice. The team departs for Nice, where for the next several days they observe the convoy and plan an ambush. During their surveillance, Deirdre and Sam pose as husband and wife and grow somewhat close. Sam observes that security surrounding the man carrying the case is airtight and that he keeps it handcuffed to his wrist at all times.
The team engages the convoy and pursues them through the surrounding highways in the country. After a lengthy car chase and gun battle, they successfully obtain the case, but Gregor betrays the team and switches the case with another, identical case that explodes, seriously injuring Larry. Gregor disappears.
Gregor attempts to sell the case to the Russians but when his contact pulls a gun, he shoots the Russian contact and kills him. Gregor contacts Mikhi, the leader of the Russians and threatens to sell the case to the Irish unless Mikhi pays a grossly inflated price for it, which Mikhi agrees to. Meanwhile, the rest of the team track Gregor through one of Sam's old CIA contacts and corner him in the Roman arena in Arles, where he is meeting the Russians. A tense standoff and hectic gun fight follows as Deirdre, Sam, and Vincent attempt to capture Gregor while the Russians try to kill them. In the melee that follows, Vincent comes face-to-face with a man he recognizes from a previous job and is nearly shot. The man is distracted by Sam and his bullet ricochets off the stone wall and hits Sam in his abdomen. Vincent shoots and kills the man instantly. Gregor escapes the coliseum. As he runs from the arena, he is intercepted and captured by Seamus, who has already killed Larry. They escape with Deirdre at the wheel just as Sam and Vincent emerge from the coliseum.
Vincent takes Sam, who was seriously wounded by the stray bullet during the fight, to his friend Jean-Pierre (Michael Lonsdale) in a villa in rural France. Vincent removes the bullet and allows Sam a day or two to recuperate. Vincent asks Jean-Pierre to help him locate Gregor, Deirdre and Seamus. Meanwhile, in a Paris slum, Seamus learns that Gregor has mailed the case to himself at a post office in Paris. Seamus and Deirdre escort Gregor to the post office where they retrieve the case, and they are ambushed by Vincent and Sam. Sam, feeling a bit of closeness with Deirdre, hesitates when he could have stopped her escape by shooting her; she gets away and picks up Seamus and Gregor. During the high-speed chase that follows, they drive the wrong way against traffic and through the streets and tunnels of Paris. Vincent finally shoots out one of Deirdre's tires. The care crashes and falls over the unfinished end of a highway overpass. Construction workers pull the three from the car shortly before it explodes, but Gregor once again escapes with the case.
Vincent and Sam, considering their options, discover that the case is identical to one used by figure skaters. They surmise that Gregor had been working with the Russians all along and that they had made the decoyed case for him. They conclude that if they can find the Russians Gregor plans to sell the case to, they'll find Gregor.
Intelligence gleaned from Jean-Pierre's contacts also suggest the Russians are involved with figure skater Natacha Kirilova (Katarina Witt), a protégé of Mikhi, who is performing in a show at the local arena that night. Vincent and Sam appear at the arena as Mikhi, already there with Natacha, receives a call from Gregor, who demands to meet in a backstage broadcasting room. At the meeting, Mikhi exchanges money for the case when Gregor, prepared to leave, reveals that he has positioned a sniper somewhere in the arena that will shoot Natacha if Gregor is betrayed before he can leave safely. Mikhi shoots Gregor anyway, and Natacha is also killed by the sniper. Mikhi and his bodyguard leave the arena with both the case and his money, blending in with the panicked crowd fleeing the arena. Vincent and Sam follow the crowd out of the arena in time to see Seamus, disguised as an arena security guard, ambush and shoot Mikhi and his bodyguard before stealing the case. Sam runs ahead of Seamus and finds Deirdre sitting in the getaway car, where he encourages her to leave. He reveals that he is after Seamus, not her and that he'd never actually left the CIA. Deirdre hesitates and asks him to leave with her, but he refuses, and she flees, leaving Seamus. Seamus' exit is blocked by the crowds. Sam and Vincent confront Seamus, but are momentarily distracted by the security guards, and Seamus shoots Vincent. He escapes through the crowd back into the arena building. Sam pursues him. Seamus wounds Sam and is about to kill him when Vincent opens fire from scaffolding above the arena, killing Seamus before collapsing from his own wounds.
Some time later a BBC radio broadcast reveals that, as a result of stability resulting from the death of the terrorist Seamus, a peace agreement has been reached between Sinn Féin and the British. Sam and Vincent share a drink in the same Montmartre café from the first scene. Vincent tells Sam that Deirdre will not be returning to the cafe. He asks Sam what was in the case. Sam replies, "I don't remember." They part as friends and Sam drives off with his CIA contact. Vincent disappears up a staircase into the streets of Paris.