Policías, en el corazón de la calle

The cops Carlos and Lucía stop a car at night, but the vehicle escapes. A persecution starts and the policemen get support from a helicopter, however the criminals take out their guns and shooting at the cops they stop the car and shoot down the helicopter managing to escape. Added by they partner Mateo, Lucía and Carlos manage to rescue the helicopter passengers, but the pilot, Goyo is in critical condition. The criminals are identified as Los Guti, two brothers that have stolen various restaurants in the zone and all the force from the station are warned that they should look out for them. Some nights later Mateo and Carlos find the pair in a street, but once again the brothers manage to escape. In other story lines rookie cop Vera is assigned to patrol with Jaime who isn't happy of having to train the new girl, both policemen doesn't get along to well, and Vera feels humiliated by her partner who doesn't support her when she accidentally kills a convenience store robber. Cops Mateo and Rafa investigate the attack on a family that refuses to sell an apartment whose owners wish to have them out to sell the property. Inspector Ferrer and his parter El Ruso arrest a gun trafficker but fail to protect their informer. An unemployed man is forced to rob to feed his daughter. Paramedics Susana and Pedro save a drug addict's life who knows Pascual, a friend of policeman Rafa who is later arrested for robbing a house. Marina saves a clown that has been tied up by a group of children at a party. Mateo's pregnant daughter gives birth to a baby girl and Lucía's starts to consider if she wants to become a mother.

Vera is investigated by internal affairs due to the killing she made in her first mission and she realizes she will need the support of her partner Jaime to be acquitted, but he doesn't want to help her. Marina is called by some neighbors due to the annoyance caused by an ex circus performer who has seen his chimpanzee die, the policewoman befriends the performer. Police chief Héctor Ferrer tries to save drug addict Bolaños and forgets about an appointment with his wife who feels abandoned. Criminal brothers Los Goyo rob another restaurant where one of them is shot, refusing to go to a hospital the wounded brother hides in an abandoned factory and forces his parter to kidnap the paramedics Susana, Pedro and Román in order to save his life, but the disappearance of the ambulance makes the policemen aware that something is wrong.

Lucía is the most important witness in a trail against a extremist that she arrested two years ago when he burned a vagabond alive, but the partners of the extremist break into her home and warn her not to testify. When she does it anyway they decide to kill her in revenge, leaving Carlos and El Ruso as part of an operative to protect her. Due to lack of results, Ferrer is ordered to drop an investigation on drug sellers in the neighborhood, but he refuses and keeps on working on his own. A Ventriloquist with a personality disorder seeks help claiming that his dummy is harassing women, he is ignored but his disorder grows to the point were he rapes a woman. Mateo and Rafa's police car is stolen by a pair of criminals that later impersonate cops to rob money. Rafa meets and fells in love with his partner Mateo's daughter. Rookie cop Vera is still dealing with the unintentional killing of a criminal, and in a mission she fails to shot his gun against some criminals putting the life of Marina in danger. Paramedic Susana seeks to help out an old man who is depressed by the demise of his wife.

Ferrer finds out the name of the new drug dealers whose heroin is causing the death of many addicts and he contacts them at a parking lot where he offers them a deal, protection in exchange of money. A mysterious man starts shooting the dogs of the people in the neighborhood, and after a while he decides this is not enough and also starts shooting their owners. Vera informs Lucía that she is considering leaving the police since she has been unable to recover from the shock of killing a man in one of her first missions, Lucía asks her to reconsider. Later she tries to help a woman who feels guilty about a climbing accident that left his boyfriend paraplegic. Carlos spots his ex-girlfriend Patricia kissing a grown up man and after following her he discovers she is a prostitute. Pedro and Rafa try to solve the issues between them that started when the paramedic found Rafa having sex with Mateo's daughter in an ambulance. Deputy Clavijo takes his nephew to visit the police station and forces an unhappy Marina to look after the child while he attends a meeting.

A news dealer accidentally runs over a little girl with his van leaving the girl badly hurt, the father of the child feeling helpless to aid her daughter decides to get revenge while police officers Jaime and Vera deal with the situation. The new drug dealers to whom inspector Ferrer has promised protection are unsure whether to trust him or not, so they ask him to help them in a operation to eliminate the rival gang; Carlos notices Ferrer's strange behavior and suspects he has been corrupted. Lucía's boyfriend visits her in Madrid and asks her to resign her dangerous job. Carlos tries to deal with the discovery of her ex-girlfriend working as a prostitute and confronts her while she works. Rafa and Pedro attend the trial of their friend Pascual, who was arrested on the first episode. Mateo deals with a homeless woman who uses to pretend she gets sick in order to be admitted at the hospital. Marina continues her relationship with hospital doctor Gonzalo.

Carlos and Lucía spot one of the Iranian drug dealers and try to arrest him, but El Ruso sees them and stops them by crashing their car, both cops start suspecting about Ferrer's involvement with the mob and decide to investigate him which puts in risk Ferrer's cover just as he has gained the confidence of the Iranians who offer to introduce him to their boss. Carlos has doubts about continuing his relationship with Patricia. Lucía receives some Saint Valentine's presents from her boyfriend, but she also receives a package form a mysterious admirer. Susana is robbed in the street and she is aided by a Dominican immigrant who is injured by the fleeing robber. Marina tries to add a mature woman who has been conned by a man pretending to love her, but convinced of her feelings the woman refuses to see she has been used. Rafa and Mateo are assigned to watch the cemetery, were several corpses have been stolen. While they are on the case Rafa continues dating Mateo's daughter, while he fears confessing this to his partner. Jaime and Gonzalo quarrel due to their mutual interest in Marina.

The relationship between Rafa and Mateo gets worse after Rafa is violently beaten by Cipriano, a cop from another precinct who happens to know Mateo. After learning that he sent a fellow cop to the hospital, Cipriano asks for Mateo's assistance to avoid being expelled from the force. Lucía finds Juan, the elderly man she assisted, and discovers he is trying to find a son with whom he fight and lost contact years ago, asking for Lucía's assistance the paramedic tries to help them become reconciled. Pedro finds Aurora, a kinder teacher, that vanishes while working due to a heroin addiction, the paramedic feels attracted to the girl and decides to help her recover, but he finds a unexpected obstacle in Aurora's boyfriend ho is forcing her into the drugs. A colonel's son is convicted to 40 years in prison for the rape and assassination of her ex girlfriend, the colonel is convinced of his son innocence and confronts Ferrer, Lucías and Carlos asking them to investigate again, the cops explain him there is nothing they can do, but the desperate father will take any measure to ensure a new trial for his son.

A church priest approaches Ferrer and El Ruso asking for help to stop a a young couple that attacked its church with satanic symbols, at first they are unable to help but they get interested in the case as they learn the couple is part of a big and dangerous satanic cult. Quique, Lucía's boyfriend, comes back to Madrid to inform her he has accepted a job in Morocco which requires him to leave the country for two years, this information puts strain in their relationship. Susana attends new cop Lucas after he suffers a motorcycle accident, however a mistake regarding the dose in the medicament she gives him may have terrible consequences on Lucas career. As the police force is assigned to stop a band of blackmailers, Carlos is assigned to do a night surveillance with Marina, the two cops remember some missions from the past and during the night some attraction arises between them. Jaime and Vera find a kid that escaped his home, after returning him to his parents Jaime is worried about the possibility of the child suffering physical abuse from his father, however when the kid is found beaten doctor Gonzalo denies the possibility that the father is responsible while the dislike between the two characters continues. Sebas, the prison warden, is assigned to patrol alongside Mateo for a short while, until Rafa is able to return to active duty. After some time in prison Rafa and Pedro friend, Pascual, is granted a weekend pass, out of jail he learns his girlfriend has been cheating on him with another friend.

After arresting Andrés, Ferrer and El Ruso investigate the satanist sect to which he belongs and they discover their relationship with some illegal organ traffickers. Jaime continues investigating the alleged physical abuse suffered by Rubén, the kid he found in the previous episode, but the child is afraid to confess his father violent behavior, and the man discovers the cop following him which makes him angry. Pedro founds Aurora once more, and the girl accepts his help to be rehabilitated, but she is unable to get away from his drug addict boyfriend, who will go to any length in order to get drugs. Susana faces some inquires about her malpractice regarding Lucas treatment. After being violently beaten by Pascual, Javi dies and the precinct issues a warrant to arrest him, Rafa faces a dilemma between helping his friend or doing his job. Fulgencio, a man that believes he is an undercover policeman, makes some illegal arrests and steals Marina's badge while his behavior threatens to get him into trouble.

Rafa's friend, Pascual is still at large and Ferrer pressures the cop to find him and turn him in. Pascual girlfriend leaves him and the escapee decides to leave the city, Rafael and Pedro know where he is heading for and go out to look for him. Ferre's wife, Carmen, gets fed up with her husband preferring his job over his family and asks for a separation. El Ruso gets a knew car and Ferrer worries about where could he get the money to buy it. Jaime continues trying to befriend Rubén so he gets the courage to admit his father is hitting him, when Rub'en's dad finds about this he ain't happy. Pedro and Susana deal with the aftermath of a sexual relationship they got after a night out. Carlos and Lucía stop a group of young criminals that are trying to rob a car, they capture one of them and manage a deal with his victim to keep him out of jail, but things won't go as any of them is planning to. A french serial killer escapes to Madrid and Mateo will have a close encounter with him.

Rocío, an a Lucía's acquaintance suffers a nervous crisis when she spots a man that raped her years ago. He has been released from prison and is a free man, but the neighborhood rejects him and Carlos and Lucía are unable to intervene. El Ruso keeps gambling and he accepts money from the casino owners, but a streak of bad luck leave him penniless and with a huge debt they want to collect at all costs. Ferrer and his wife discuss the terms of their separation. Marina, Jaime and Vera are assigned to an undercover mission in order to trap a man that is robbing couples in a park, however Jaime and Vera feel quite awkward acting as boyfriends. Mateo tries to catch con man Joe, but while he is chasing him Joe suffers a heart attack. Pedro reveals to Rafa he has been sleeping with Lucía, but the paramedic finds out about this and gets quite annoyed at Pedro. The bank robbers Carlos and Lucías faced some episodes ago strike again.

El Ruso tries to get money to pay his money debts as his creditors pressure him to pay. Carlos and Lucía deal with the family of a schizophrenic man whose disease led him to dangerous behavior. Quique, Lucía's boyfriend returns trying to make plans for his future with the cop. Mateo and Rafa help Dorita, the beggar whose money has been stolen. Lucía and Pedro suffer an accident while trying to get a patient to the hospital. Marina deals with an attempted robbery in a beauty parlor. The Iranian drug dealers that Ferrer infiltrated and jailed return to get revenge on the inspector by striking that which is most valuable to him.

After a failed attempt to stop the Iranian drug lords that have kidnapped her daughter, Ferrer is contacted by them again, and this time he doesn't let his partners know about this as he goes to face his enemies alone. Lucía announces she will leave the precinct to live in Almería, much to the surprise of all her partners. Carlos and Lucía get important information that may led to the capture of the two bank robbers that have been at large during the past episodes. While Vera struggles with her growing feelings toward her partner Jaime, she receives a visit from her father, a policeman from Canarias, who patrols with them to her dislike. The robbers from the first episode, Los Guti, return to face their trial, but after escaping, the force of the whole precinct and an enormous sacrifice will be needed to stop them.