The film is constructed from three distinct stories linked by a car crash that brings the characters briefly together.
Octavio y Susana Octavio (
Gael García Bernal) is in love with Susana (
Vanessa Bauche), his abusive brother Ramiro's (
Marco Pérez) wife who he has a child with. She confides in Octavio that she is pregnant again, and he tries to persuade her to run away with him, saying he will help raise her children with her. Local thug Jarocho, happy after winning in a
dog fight, intends to set his dog loose on some strays but is threatened by a homeless man wielding a
machete. Instead, Jarocho sets his dog on Octavio's
rottweiler, Cofi, but his own dog is killed. Octavio and his friend Jorge (
Humberto Busto), realising Cofi's potential, become involved in the dogfighting scene. Octavio makes enough money to flee with Susana, and pays Mauricio, the owner of the dogfighting venue, to get Ramiro beaten up. Afraid, Ramiro steals the money and leaves with Susana. Struggling financially, Octavio accepts a challenge by Jarocho to participate in a private dogfight, with no outside bets. Cofi is about to win, but Jarocho shoots him. The infuriated Octavio stabs Jarocho in the stomach. Pursued by Jarocho's thugs, Octavio finds himself in a car chase with Jorge and the wounded Cofi. A collision follows; Jorge dies and Octavio is badly injured.
Daniel y Valeria Magazine publisher Daniel (
Álvaro Guerrero) leaves his family to live with his lover Valeria (
Goya Toledo), a
Spanish supermodel. On the day they move in together, Valeria's leg is severely broken in Octavio's car crash and she is unable to continue working as a model. As Valeria is recuperating in Daniel's apartment, her dog Richie disappears under a broken floorboard and becomes trapped. The missing dog triggers tension and arguments for the couple, leading to doubts about their relationship on both sides. Trying to rescue the dog, Valeria again injures her leg; Daniel finds her hours later. Valeria's new leg injury results in severe
arterial thrombosis and eventually
gangrene. Her leg is
amputated. While she is in the hospital, Daniel finally rescues Richie from the floorboards. When she returns, Valeria drives her wheelchair through the torn-up
lovenest and looks out of the window expecting to see a billboard bearing her likeness, only to find it has been removed.
El Chivo y Maru The homeless guy occasionally seen in Octavio's story is revealed to be a professional
hitman called El Chivo (
Emilio Echevarría). He is a former private school teacher who was imprisoned after committing terrorist acts for
guerrilla movements. He is trying to make contact with his daughter, Maru, whom he abandoned when he began his guerrilla involvement and who believes that he is dead. He is about to perform a hit on a businessman when Octavio's car crash interrupts him. During the chaos at the car crash, he steals Octavio's money and takes the wounded Cofi to his warehouse hideout to nurse the dog back to health. One day, while El Chivo is out, Cofi kills all the other mongrel dogs El Chivo is caring for. He is about to kill Cofi, but decides against it. Meanwhile, Octavio's brother Ramiro is shot and killed during an attempted bank robbery. At Ramiro's funeral, Octavio meets Susana, and again attempts to convince her to run away with him, but she angrily rejects the notion. A few days later, Octavio is shown waiting at the bus station for Susana. She never shows up, and Octavio does not board the bus. El Chivo learns that his client and his intended victim are half-brothers. He leaves both men alive and chained to separate walls with a pistol within reach between them, their fate left uncertain. He then breaks into his daughter Maru's house and leaves her a large bundle of money along with a message on her
answering machine explaining what happened to him. When he is about to tell Maru that he loves her, the answering machine stops recording. He then goes to an autoshop, where he sells the client's
SUV. The mechanic asks him the dog's name, and El Chivo calls him "Negro" ("Black"). After El Chivo receives the money for the car, he and Negro walk away, disappearing into the horizon. ==Cast==