The film begins on a rainy night in London. A young Turkish youth named Ekrem (Josef Altin) walks into Azim's barber shop, where Azim (Mina E. Mina) is cutting the hair of Soyka (Aleksandar Mikic) a Russian man. Ekrem locks the door, closes the shades, and changes the sign from open to closed. He is Azim's nephew and is introduced to Soyka, but he gets extremely nervous. Azim gives his nephew a razor blade, and urges him to follow through on their plan. Soyka realizes whats going on, and tries to leave but is held down. Ekrem slits Soyka's throat, causing him to suffer painfully before he dies.
Elsewhere, a dazed young Russian girl named Tatiana (Sarah-Jeanne Labrosse) walks barefoot into a convenience store and asks for help. The clerk assumes that she's a drug seeker, and then blood starts to flow down her legs. Tatiana collapses, and is taken to the hospital. The doctors see that she's pregnant, and perform surgery to save the baby. Tatiana dies, while the baby lives. A nurse, Anna (Naomi Watts), announces the death and looks after the baby. Anna goes home and gets some sleep. She lives with her mother Helen (Sinead Cusack) and her Russian uncle Stepan (Jerzy Skolimowski).
On Christmas day, Helen wakes up Anna for breakfast. Stepan is reading a diary in the dining room, and asks her where she got it. Anna says that she took it off of the dead girl. He says that she's stealing from the dead, and that the dead girl's secrets should be buried with her. She wants him to translate the diary, since its in Russian, but he refuses. While skimming through the pages, Anna comes across a business card for a Trans-Siberian restaurant.
Anna rides her motorcycle to the restaurant, and parks in front. Nikolai (Viggo Mortensen) and Kirill (Vincent Cassel) walk through an alley, joking around, when they see Anna securing her (Russian) Ural motorcycle. They both eye her, and then Kirill orders Nikolai to retrieve Azim and his wife, and bring them to the restaurant. Nikolai drives off, and Kirill enters the restaurant. Anna knocks on the door, and its answered by the manager Semyon (Armin Mueller-Stahl), who's also Kirill's father. Semyon tells Anna that the restaurant is closed, but she tells him that she's a midwife and wants to speak to him about Tatiana. He allows her to enter after she tells him her last name, and they walk through the restaurant while Anna notices that all the workers are getting ready for a big party (while also noticing Kirill drinking at the bar). Semyon notices a couple of little girls playing the violin, but he tells them to be better and shows them by playing a tune. Anna shows Semyon the business card, and he tells her that it's an old one, and that he doesn't know Tatiana. She might have just eaten there once and liked the food, which Semyon has Anna taste. Anna wishes to find out where Tatiana's family lived, but he claims he doesn't know. He's sorry that he couldn't be of more help, and she tells him that shell probably find out more when she gets her diary translated. Semyon volunteers to translate the diary himself, and tells her to bring it to him tomorrow night. Before she leaves, Semyon makes sure to know where she works.
Outside, Nikolai pulls up to the restaurant with Azim and his wife. He stays outside by his car, which is parked right next to Anna's motorcycle. Anna comes out and he compliments her on the motorcycle. She says that it belonged to her father, and he asks if she'd be interested in selling it. She says that it holds sentimental value to her, and then he asks if she's going to stay for the party. She says no, and since Nikolai is not allowed inside because he's just a driver, he asks her if she wants to go get a drink. She speeds off without answering him.
That evening, Anna is back home and eats dinner with Helen and Stepan. Stepan gets a bit drunk, and asks how long she's going to stay with them. Helen gets after him, and tells Anna that she can stay as long as she likes. Anna just broke up with her boyfriend, which is why she's living with them. Stepan voices his disdain for her boyfriend, since he's black, and says that interracial couples shouldn't be together. He then says that's probably why Anna's baby died inside her, which greatly upsets her as well as angers Helen.
Meanwhile, back at the restaurant, everyone is enjoying themselves and drinking when Kirill gets a phone call. He moves to a quieter place to talk, and asks if the coast is clear. The caller tells him that it is, and Kirill signals to Azim that everything's fine. Nikolai drives Kirill and Azim to the barber shop, and Azim wants Nikolai to wait outside. Kirill refuses, since Nikolai works for him and is helpful for the job. They walk inside and are startled by Ekrem, who's ecstatic that he got tickets to a big soccer game. Azim sends him on his way, and assures them that he wont speak about their presence. They go to a freezer, where Soyka's body is. Kirill eats some peanuts and jokes about the frozen corpse, also saying that the man was like a brother to him. Azim tells him to show some respect, but he pulls out an envelope full of cash and says that money is respect (he gives Azim the envelope). Since the body is so stiff, Nikolai asks for a hair dryer. He places the corpse on a table and uses the dryer to thaw the body. He pulls out his wallet and gives it to Azim. He then has Azim and Kirill leave, since it's going to get a bit nasty. Nikolai puts out his cigarette on his tongue, and then cuts off all the fingers and removes the teeth from the corpse. Nikolai and Kirill drive out to a waterfront, and they throw Soyka's wrapped up body into the river, where it sinks.
Anna gets ready for work when Stepan and Helen walk into her room. Stepan tells her to be careful with the diary, since he's read the words rape, prostitute, and needle.
Nikolai and Kirill go to a whorehouse to party. A lot of the girls look underage, but none of the customers care. Kirill is drunk, and licks a girl who's dancing on a pole. He then sits on Nikolai's lap, who's making out with a prostitute. He asks him which one hes going to sleep with, but Nikolai tells him that he'll pick when he's ready. He continues to make out with the prostitute but is interrupted again when Kirill smashes the stereo with a bottle. Kirill wants to make sure that Nikolai's not gay, and says that hes going to watch him have sex with one of the whores. Forced to pick, Nikolai chooses a prostitute named Kirilenko. He has sex with her while Kirill watches, and then when he's done Kirill claps. Nikolai tells him to go away while he changes. Kirilenko sings to herself, and Nikolai asks her what her full name is and where she's from. He gives her a wad of cash and tells her to live longer.
Elsewhere, the police have found Soyka's body. The lead inspector goes into a tent to view the body. He sees that Soyka was part of the vory v zakone, a brotherhood of criminals. Each member is tattooed while in Russian prison, with each tattoo having significance. Upon seeing his tattoos, the inspector deduces that he was a captain of the vory v zakone, and that he knelt to no one. Another curious thing that catches his eye is a note inside of Soyka's jacket.
Anna goes to Semyon's restaurant, and he's surprised by her coming early. She apologizes, and he welcomes her inside. She has photocopied Tatiana's diary, and gives the pages to Semyon to translate. He asks her where the original diary is, and she tells him that she wants to give it to Tatiana's baby when she's old enough. Semyon says that he broke his own rule; he drank vodka, and so since he's not sober he will translate the diary tomorrow. He asks her where she lives, but she says that she can come by again for the translation. As she leaves, Nikolai pulls up with a very drunk Kirill. Semyon closes the door on them, and Nikolai opens it using Kirill's key. Kirill is so drunk that he cant even stand up, and so he falls on the floor and rests his head on Nikolai's foot. Semyon, disappointed, walks over to Kirill and kicks him a couple of times. Nikolai tries to stand up for him, but Semyon puts him in his place. Nikolai goes outside and hears Anna in the alley, trying to start up her motorcycle. He tries to help her, but finds that the motorcycle is dead. He offers to drive her home, since its raining outside and Semyon would get after him if he let her walk home.
While he drives, Anna asks him if he knew Tatiana. He says that he knows a lot of girls named Tatiana, but no pregnant ones. She then asks if Kirill knew her, and he tells her that he's just the driver. When they pull up to her home, she asks him what he wants in return. Nikolai says that he wants a Christmas present, and then leaves.
While at work at the hospital, Anna watches over the baby, who she has named Christine, and gets emotional thinking about her own dead baby. Semyon surprises her, and when she asks how he got in he says that there are always open doors. She tries to get him to leave, but he says that he has translated the diary. He is most disturbed that Kirill is mentioned several times, including details about some illegal activities he has done. He asks that Anna not go to the police with the diary, claiming that Kirill is a good boy and that he will deal with him on his own. Before he leaves, he looks after Christine and remarks on how perfect she is.
Anna goes home, and sees that Stepan is reading the diary out-loud while Helen writes it down in English. The passage details that Kirill threw Tatiana down the stairs and beat her. He tried to rape her, but when he found that he couldn't he wound up beating her some more. Semyon then proceeded to rape her and gave her a bunch of pills afterwards. Semyon is Christine's father. Anna tells them that Semyon translated the diary, and threatened the baby. In return for handing over the diary, Semyon promises to give Anna the address of Tatiana's family. Stepan gets after her for being so foolish, and since the baby is being threatened Helen and Anna agree to make the deal with Semyon.
At the restaurant, Nikolai and Kirill receive a shipment of old alcohol in a truck. Nikolai asks where it came from, and Kirill says that if his father agrees, they'll let Nikolai deeper into their family and their business. Semyon appears and gets after Kirill for Soyka's death. Kirill denies having any involvement, but Nikolai tells Semyon the truth (that Kirill paid to have him murdered, and they got rid of the body). Semyon says that if anyone is to be killed, he doesn't want to be the last one to find out. He also mentions that Soyka's brothers might come looking for revenge, but Nikolai says that he will protect Kirill.
Meanwhile, Anna, Helen, and Stepan go to a restaurant and drink some coffee. Nikolai walks in and sits down at their table. Stepan says that he used to be with the KGB, and knows how to deal with scum like Semyon. When things get cooled down, Nikolai asks for the diary (he's been sent by Semyon). Anna slides it across the table, and Nikolai puts it in his jacket. When she asks for Tatiana's address, Nikolai ignores her and walks outside. Anna runs out and demands to know the address. He tells her to forget any of this ever happened, to stay away from people like him, and to go back inside with the good people. Helen comes outside and brings Anna back inside the restaurant. Stepan spits in Nikolai's face, and Nikolai gestures that he's going to kill him via sticking his fingers underneath his throat and pointing at him.
Nikolai goes back to Semyon's restaurant, and reads Tatiana's diary. Semyon is happy that he has retrieved it, but is concerned since Stepan has already read the diary, and orders Nikolai to kill him. It's also revealed that Soyka was killed because he was spreading rumors of Kirill being queer (homosexual). Semyon douses the diary with vodka and burns it while Nikolai looks on.
The next day, Ekrim goes to the soccer game and his team loses. While walking down the street with a mob of fans, he stops in a graveyard and pisses on a grave. Two men approach him, one of whom is Soyka's brother, and slit his throat in broad daylight.
A little later, Nikolai stalks Stepan to his home and follows him inside, where it's implied that he kills him. Nikolai then goes to the hospital and waits for Anna to get off of work. He reveals that he read the diary, and she asks him how he can still do what he's doing and be okay with it. He changes the subject and gives her the address of where Tatiana's family is. He says that its not a good place for a little girl to grow up in, and suggests that Anna just take care of Christine herself.
In back of the restaurant, Semyon meets with Azim, who tells him that Soyka's brother has killed Ekrim. The brother has decided to spare Azim, but in return he must give up Kirill (who ordered the hit on Soyka). Semyon is not pleased with this, but tells Azim to inform the brother that he will do as he is told.
That night, Anna waits outside the restaurant when Nikolai and Kirill pull up. Kirill orders her to go away, and orders Nikolai to stop seeing her. She tells them that Tatiana was just 14-years-old, but Kirill will hear none of it and goes inside. Nikolai tells Anna to go away and not get further involved with trying to learn more about Tatiana. Nikolia then enters the restaurant.
As Nikolai and Kirill walk through the kitchen, Kirill mentions that the police raided the whorehouse, and asked for Kirilenko by name. They meet up with Semyon, who tells Kirill to go away while he talks with Nikolai on his own. Kirill, a bit hurt, storms off downstairs to get drunk. Nikolai tells Semyon that he killed Stepan, which pleases him. Afterwards, Nikolai goes downstairs and has a drink with Kirill. He says that Semyon offered him the opportunity to get his star tattoos, and he accepted. Kirill embraces him, and tries to come off as if it was his idea for Nikolai to get the stars (though its obvious he didn't know until he told him).
Later on, several members of the vory v zakone arrive at the restaurant and are greeted by Semyon. Nikolai is seated in front of them wearing nothing but his underwear. The members inspect the tattoos he received while in prison, and review Nikolai's criminal and family history. Nikolai renounces his parents, and is then given the star tattoos on his shoulders and knees.
The next day, Azim meets with Nikolai at a bathhouse to discuss some business. He says that it's a preferred meeting place, since everyone can see the tattoos they have. Azim and Nikolai dress down and wear towels. Azim excuses himself to use the restroom, and instead starts to get dressed again. Two thugs come in, and Azim tells them that Nikolai is Kirill (they don't know what he looks like). They spare Azim and walk into the sauna, where Nikolai is naked except for the towel on his head. A thug pulls out a knife and slashes his chest. Nikolai beats him up and wrestles for control over the blade. After that fails, he tries to crawl away but the other thug is waiting for him and slashes his body with another knife. Nikolai makes one of the thugs stab the other in the chest, and then brutally brawls with him on the floor. He gets his hand on a knife, places it underneath the goon's head, and smashes his head onto the blade. Nikolai, beaten and bloodied, starts to weakly crawl away. It turns out the other thug isn't dead yet, and he starts to choke Nikolai with his bare hands. The thug rips out the knife from his chest and tries to use it on Nikolai, but he gets the upper hand and stabs the thug through the eye.
A little later at the hospital, Anna sees the extremely wounded Nikolai being carted down the hall. She enters his room and asks him if he knows where Stepan is. If he doesn't turn up soon, she'll get the authorities involved. Nikolai reveals that he was sent by Semyon to kill Stepan, but he didn't. Instead, he sent him to Edinburgh and set him up in a hotel.
The police inspector who found Soyka's body arrives at the hospital and privately talks with Nikolai. It's revealed here that Nikolai is really an undercover MI5 agent hired to infiltrate the vory v zakone. The note he put in Soyka's jacket was a progress report, and he called in the raid on the whorehouse to help out Kirilenko. The inspector says that Scotland Yard and the KGB/FSB are not happy with Nikolai's job handling, and when he sees his star tattoos he is worried that he has perhaps gone too far undercover. Nikolai reassures him that everything's fine, and that he can even become head of the vory v zakone in London. The inspector balks at the idea, but Nikolai tells him that all they have to do is arrest Semyon. When he asks for what charges, Nikolai tells him that the charges will be the rape of the 14-year-old Tatiana. Since she's dead, she can't testify, but they can prove Semyon is the father of the baby through blood tests.
Meanwhile, Kirill is inflating balloons for another party when he notices a little girl staring at him. She asks him if he fought with Semyon last night, because she could hear shouting and banging. Kirill says that its not a fight if one of them doesn't fight back, and says he was upset upon learning about Nikolai's attack (orchestrated by Semyon). Kirill then sees several policemen arriving outside the restaurant via security monitor, and tells the girl to go upstairs. After the cops leave, Kirill asks Semyon what the cops wanted with him. They took a blood sample from his arm, and Kirill asks him why they would want that.
As Anna gets off of work, she sees Kirill in a closing elevator holding a gym bag. She rushes to the baby ward and finds flowers in place of Christine. Anna bumps into Nikolai again and harshly demands to know where Kirill took the baby. He honestly doesn't know, and so they both head out in search of Kirill, who goes back to the waterfront where Soyka's body was dumped. He picks up the gym bag, which has Christine inside, and sits by the water. He cries, and asks for forgiveness. He's about to throw Christine in the river when Nikolai and Anna arrive. Nikolai tells Kirill that Semyon has gone too far, and they don't kill babies. He then forces Kirill to choose between him and Semyon. Kirill embraces Nikolai and says that he didn't know that Semyon set him up at the bathhouse. Nikolai says that he understands, and gives Christine to Anna. Nikolai then tells Kirill that his time to control the family is now, and they can be partners with Semyon out of the way. Kirill becomes cheerful again, and tells Nikolai that they should go out to celebrate, since it's New Years Eve. Kirill walks off and waits for Nikolai. Anna demands to know who he is and why he helped them, but Nikolai simply replies that he couldn't be king if the king was still in place. They briefly kiss each other, and then Nikolai walks off with Kirill.
Some time later, we see Helen and Stepan fixing lunch while Anna plays with Christine (she adopted her). Semyon is presumed to be in prison for Tatiana's rape. The final shot shows Nikolai sitting alone in the restaurant, leaving his future unclear.