FBI season 4

A man is murdered in Budapest, and the shooter re-emerges in New York where he shoots a woman, Nicole Wyatt dead after she has attended a yacht party. The FBI team uncovers that Wyatt was the pimp in an underage sex trafficking ring, targeting rich people. The girl she was with before being murdered, Julia Walcott who's also fifteen years old, is reported missing, but later re-emerges before being kidnapped by the shooter. However, Julia is soon found at a warehouse, injured, having been shot twice in the chest and later dies while on the way to the hospital although not before she urges OA to find her friend, Sunny. The Most Wanted team's Kenny Crosby soon joins Bell and Zidan in taking down the kidnapper, former veteran Curt Williams, but is severely injured, a move that soon has Bell clashing with Crosby's supervisor, agent Jess LaCroix. Williams identifies Nathan Tate as the culprit, but as Bell, OA, Scola and Tiffany prepare to head into his building to arrest him, he is shot dead by an unknown individual and thrown from his office building, OA identifying Tate due to the gold watch on his wrist.

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This episode begins a crossover event that continues on the season 3 premiere of FBI: Most Wanted and concludes on the pilot episode of FBI: International. while Julian McMahon (Jess LaCroix) and Kellan Lutz (Kenny Crosby) are credited as Special Guest Stars

New York Children's Hospital is put on system lockdown after suffering from a cyberattack. Jubal's son, Tyler, is also being treated there. The FBI soon learns the demand from the hacker, which is unusual with it being for them to track down an alleged serial killer, who has killed recently discharged patients from a psychiatric hospital. They stop a man, Jason Cooke, who planted the malware at six other hospitals as well. Through patient records, they narrow the hacker to be Lydia Ryan, who sent complaints following her roommate's death. She refuses to lift the hack despite Jubal bringing his son up. Subsequently they pinpoint the psychiatric hospital's Secretary assistant, John Maguire (born Mullen), as the suspect. Wallace and Scola prevent him from killing another recently discharged suspect, and the FBI corners him in a storage facility. Initially Ryan accuses them of manipulation, until Maggie convince her by mentioning her own sister's rehab. Tyler goes through a successful surgery after power is returned to the hospital while Trenholm informs Bell and Castille Ryan will be charged with murder due to an eleven year old girl dying from a collapsed lung which the doctors couldn't detect due to the equipment being off at the time.

A bomb detonates at the Federal Courthouse, having been planted in the bag back belonging to a young boy. Surveillance cameras help the FBI in identifying the suspect as Ryan Davis, a veteran. Despite refusing to talk to them, further background checks lead the FBI to a veterans club, the Garrison Lounge, who has also been on the ATF's radar. Castille asks O. A. to ask his friend, fellow veteran Chris Zapata, to go into the club with a wire to get them an inside view of the club. Facial recognition from Zapata's button cam, lead them to the bomb maker, Victor Maxwell. Furious that there was not enough evidence to take down the club owner, Nick Hawthorne, Zapata returns to the club and takes Hawthorne hostage. Despite surrendering, Zapata shoots and kills Hawthorne by shooting him three times in the chest as he tries to disarm him, leaving OA stunned and Bell arresting Zapata.

The murder and subsequent discovery of Rob Holden, leads the FBI to track down a serial killer who prays on young homeless black men, with a spree lasting the last two weeks. The killer's description matches Isaac Jones, but despite this, he's quickly ruled out as a suspect, but is later found dead at the hands of the killer. Scola discovers that Tiffany's cousin, Terrence, was at the club where Holden was before being killed, setting the suspicion on him. Off the record, Tiffany learns that Terrence suspects he is gay, which was why he went to the club. Suspicion against him increases when the FBI learns that a blue van, which is also owned by Terrence's church, was used in kidnapping the victims, as confirmed by a victim who escaped. Tracking the whereabouts of the club's guard, Greg Robinson, the FBI determines that he was at the forest dumping sight. Scola discovers another victim nearly alive, as Robinson arrives and attempts to kill him, but is stopped by Wallace, the two men both dying. Castille gives her a warning for taking part in an investigation with a conflict of interest. Scola and Wallace agree to talk more and be more open in their partnership.

Charlotte Kincade is kidnapped from her suburban home while her husband, Alex, is away in Newport. As the FBI's New York Office look into the case, they quickly discover that Alex was not being honest about his Newport trip being business related, and that he saw another woman, Jamie Barker, with whom he had an affair. Looking through Charlotte's last movements, they discover she was chased away from an ATM by Grant King, who reveals the “chase” was a mere fantasy experience, and Charlotte was played by another woman. The New York Office also discovers that Charlotte was a member of the same sex club as King, which her husband was not aware of. They identify the suspect as high school drop out, Andrew Frazier. Frazier escapes as Scola and Wallace attempt to apprehend him. The team also uncovers a house with specifically decorated rooms to his victims, one of them being Brenda Mason. With Alex's help, the team track down Frazier to an inn which Alex and Charlotte once visited. O. A. convinces Frazier to release Charlotte and manages to disarm him in the process. Despite Mona's suggestion for him to change careers, O. A. remains firm on working for the FBI.

NYPD detective James Gerrard from the 27th Precinct is shot and killed outside a bar. Soon after, a fellow detective, Aaron Dane, from the same precinct is shot, but survives. The FBI take in career criminal Rafael Alvarez, who explains that he gave a warning to Gerrard and Dane about money they stole from a raid, that belongs to a crime family. They learn that another detective, Pat Rudinsky, was sent to prison after having been forced to take $10,000 of said money, having also told the truth to his son, Ray, who is also identified as the killer, taking out police members that were involved in sending his father to prison. Ray takes Wallace and officer Michelle Ruiz hostage and demands to see Dane. Dane and fellow detectives arrive on scene, but are held back, promising to step in the second the FBI begin screwing up. After Ruiz reveals the truth of her involvement in his father's case, the FBI storm the residence, and Scola neutralises Ray. Wallace later decides to open a case against Ruiz and others involved in the case.

Note: This episode refers the 27th Police Precinct, which is the location of Law & Order.

Lucia Diaz is abducted from her daycare centre, while on the surface her parents seem to have a clean record. However, her mother, Jenny, later steals jewellery from a former nanny employer in order to help her husband, Hugo, pay of a debt he owes to the Queensbridge local Latin Kings leader, Ricky Moreno. Wallace and Scola find Hugo in a park, high on drugs prior to his meeting with Moreno. He cooperates with the FBI and wears a wire while meeting Moreno. Maggie is distracted when she learns that her sister, Erin, has overdosed, resulting in a narrow escape for Moreno, who shoots Hugo and a police officer in the process. O. A. discharges her from the mission so she can tend to her sister. A previously interrogated suspect, Tito Velasquez, is revealed to have been a look out for Moreno, and Castille convinces him to reveal the former's location. The FBI storms the warehouse, arrest Moreno and his goons and saves Lucia. Maggie decides to distance herself from Erin while she undergoes a second round of rehab, Jubal informing her that if the police officer had died, she would have been out of a job and telling her that what happened the previous day cannot happen again.

Elliot Young, a former veteran and bomb technician, is shot in his home and crawled outside before dying. The FBI and NYPD discover a hidden lab in his basement, used for making bombs. A stolen car leads them to Hannah Thompson, whose boyfriend, Alberto, is revealed to be a part of a Venezuelan socialist revolutionary movement, and real name being Felix Ramos. Thompson meets his friend Ernesto, to deliver money for their staged film company, before the FBI intervenes. A second meeting puts Thompson face-to-face with Carlos "the Jackal" Velez, who attempts to force her into a car. The team tracks down Ramos, who reveals a bomb has been planted at Thompson's workplace. Scola uses Ramos’ brother Pablo, as leverage for him to give up the code. Afterwards, Wallace encourages him to move forward from thoughts of his brother having died on 9/11, and he finally decides to meet his brother's wife again.

Trenholm is shot when she and Jubal are about to head to work, being in a critical condition. Through her surveillance footage, Jubal and the team discover that someone followed her to work one day, a man named Castlewood, who reveals to be working for someone higher up that both he and another associate, Logan Winters, won't cross. Winters manage to evade the FBI at multiple turns. Despite ATF objections, Jubal gets a warrant for them to search a gun store owned by Bill McCain. McCain reveals that Winters and their higher up, were both in the same prison prior to the former's release. McCain had also been tasked to build several automatic gun boxes with built in facial recognition that would target all FBI agents involved in a case, including Castille and Jubal. They learn that the one who orchestrated the assassination of Trenholm is Antonio Vargas, who they had previously locked up. Vargas reveals his motives to be revenge against the FBI after his wife and child were murdered and hanged on a bridge in Mexico. The team manage to corner Winters, who takes a hostage before being shot. He also tells Jubal about the remaining boxes.

Armed robbers rob a jewellery store, killing the shop owner and a woman in their escape. The FBI manage to find several stolen fake watches in a box in a pawn shop, where the shop owner was killed. Nearby traffic cameras point to 16 year old Jamal Carter who was the last person to carry the box. The FBI's suspicions turn to his three older brothers, and with permission from child services, have him wear a wire to his house. The connection is lost for a brief second, but Bell and Wallace have a hard time getting Jamal to tell them the truth of what happened. The FBI discover a secret room in his foster father's room, containing weapons of different sorts. They deduce that he assisted the older brothers in the robberies. Him and the brothers rob a bank and hold people hostage. Through their escape, they send out smoke grenades as a distraction, but are still caught. Scola reveals to Bell that Wallace was the officer who shot Jamal's biological father on Christmas Eve seven years ago, something she feels guilty about.

Trenholm passes away, and Jubal returns her belongings to her mother, Nicole. The FBI investigates the recent abduction of 19 year old Angela Mullins, and track the car she was dumped in to Long Island, where a victim escapes but is hit by a truck. The victim is identified as Cassidy Drabeck, who had been reported missing by her father for four months. Further evidence establishes a club owner, Beth Paige, as an accomplice to kidnapper, Doyle Buckler, who Paige tries to protect. Buckler's motive is retaliation against his first date, Darcy Edmonds, by kidnapping girls who share a similar appearance to her. Jubal takes a personal interest in securing justice for Cassidy's father, but he is outraged for Buckler having to wait a year before trial. After Buckler's arrest and hospitalisation, he takes a hostage at the hospital, before he is talked into surrender by Jubal. Later, Jubal returns to Rina's office and upon sitting down at the desk, breaks down in tears, mourning Rina's death.

Maggie goes undercover at a bar, after its owner, Colin McConnell, suspects some of its customers, schemes about utilising bombs in attacks that previously killed an NYPD inspector. The councilman for the district, Doug Archer, is killed in another bombing at his office. Jubal and the rest of the team track the delivery man, Brian Markham, who reveals another man gave him the package in exchange for 100$ dollars. The man is identified as one of the extremists, Eric Park. Despite a rejection from McConnell to wear a wire, Maggie decides to plant listening devices in a private room in the bar, which is later made by the extremists. As their leader, Dominic Lawson, heads to warn McConnell, Maggie and OA rush to stop him, arresting him. Park and James Wright, drive a truck to a shelter where Lawson's sister was killed. The FBI manage to arrest them and Maggie brings the truck to an isolated dock before it detonates. An enraged McConnell accuses Maggie of intentionally endangering him and his family for the sake of the case, and decides to move to New Hampshire.

Pakistani student Kosey Khan and his brother Amir are assaulted by masked men in their apartment, leaving the former dead and the latter with serious injuries. The FBI suspect James Tinker, a janitor who had continuously narrated the Khans, suspecting Kosey of stealing. This proves true as he had stolen parts to make plastic guns to someone. OA works with special agent in charge for counter terrorism, Rashid Bashar, to talk to his local imam, Mustafa, about the suspects having visited his mosque. Bashar pushes the limits, leading to Mustafa filing a complaint. The suspects are identified as Chechen nationals Tapa and Rasul Petrov, who are seeking revenge against former Russian general Dmitry Borchin for a massacre in their village. Maggie and OA manage to stop Tapa, but Rasul escapes. The FBI rushes to Borchin's seminar in Brighton Beach, and manage to disarm Rasul as he aims on Borchin. Castille puts Mustafa's complaint to Bashar and OA, the former dismissing it. OA decides to support Bashar instead of Mustafa.

A bomb detonates in the building of Jamie's Foundation led by anti-gun activist Ann Tasker whose daughter, Jamie was killed ten years ago. The FBI discover that Gotham Freedom Front had encouraged attacks against Tasker, although its leader, Paul Bogsen, does not condone violence. He does however point them to David Moder, someone he labels a loose cannon. After Moder escapes during a protest, he's tackled by two NYPD officers who continues to beat him. Wallace reports the incident to Internal Affairs, but Bashar asks OA to water it down if he were to get a promotion. In Moder's storage room in Hackensack, the FBI discover a bomb lab. Moser points them to someone dubbed Wally who also helped with the bombs, revealed to be Walter Forrest. He points them towards an unknown person he met on the GFF chat board, whose IP is revealed to belong to Tasker. Another bomb detonates at the empty offices of the newspaper The Sentinel, killing three teenagers who had broken in. A hostage situation occurs at GFF, with Bogden's assistant taken hostage by Tasker. Maggie manages to talk her down, pointing to her actions being the opposite of what she wanted to do. OA speaks to Internal Affairs and remains firm on Wallace's side of the story, that Moder's arrest was an assault.

Twenty nine year old Violet Kent frantically attempts to enter a bar, and asks the woman on duty to call the police. A mysterious man breaks in and kidnaps Kent. The FBI investigates and receives the bar woman's witness account, describing a muscular man with black hair kidnapping Kent. They identify a man who was aggressive to Kent at a bar the night before, Bobby Gannon, but he has an alibi. Kent is later found dead and further evidence shows a string of four victims in several cities across the country, with Kent being the first in New York. They bring in Dwight Maddux, who also matches the description, but he points them towards a Latino man matching the description. Said man is identified as Andres Silva, a MMA fighter. Silva's assistant points them towards his brother, Eduardo, but he also has an alibi. Castillo approved a sneak warrant into Silva's hotel penthouse, much to her father's dismay, who owns the hotel chain. Tiffany and Scola attempt to arrest Andres at the gym, but he isn't present, while his assistant is also missing. She is later found dead in Queens and Andres escapes. Eduardo explains to OA and Maggie how they were both abused by their father as kids, which impacted Andres the most. Prior to their Miami visit, his girlfriend had also dumped him. Castillo is informed that Andres is headed to an airfield in Farmingdale. There, OA and Andres get into a fight where he almost strangled OA before Maggie disables him. Castillo's father asks her out for dinner and that they reconcile their relationship, which she accepts.

Right before the start of a charity event hockey game, a sniper opens fire, killing ICE agent Mike Mulder while also injuring other people present, with congressman Curtis Grange and his son Ethan also in attendance. The investigation leads to a local gunsmith, Jim Weaver, who gives Scola and Maggie a list of his clients and the ammo they purchased. The list points them to Bradley Baker, who has a Facebook Wall full of messages and posts about abolishing ICE. Wallace and OA go to question him, only for Baker flee on his motorcycle. Grange releases a video about his opinion of the shooting. The team analyse the gun and realize that Baker's rifle couldn't have been the one used, but a semiautomatic rifle, ruling out Baker as the shooter. Immigration judge Alvarez was shot down while Baker was in custody, it was the same modus operandi as the first shooting. The team discovers a connection between the victims and the assailant, Oscar Rodriguez, who was romantically involved with Baker. Rodriguez's parents were deported and later murdered by the local MS-13. Rodriguez successfully targets Grange at a campaign gathering. Baker is brought in to talk him down when he takes a hostage. He's unsuccessful and OA is forced to shoot him. OA offers Ethan Grange an application to join the FBI when he's of age, and reassures him that he will help him with the process when he's ready.

John Kraus and Julia Miller are killed by a masked assailant at the General Grant National Memorial. The FBI discover that they had returned from a trip to Cancún, which not even Miller's mother knew of. Medical examination reveals that she had smuggled cocaine in her body, and the driver who drove her and Kraus is identified as Benny Gomez. Scola and Tiffany learn that he was working with Nina Chase, an undercover agent and a former date of Scola. The team learn that Gomez was her informant in order to take down the Mexican Regents headed by Hector Garcia, known as El Perro. Gomez is cleared from the case, and the director orders Chase's investigation to be merged with Castillo's after it becomes obvious that the cases are related. Gomez goes in with a wire and manages to convince Garcia's enforcer Octavio Lopez to meet Chase. At the meeting, she lands a deal with him and to subsequently meet Garcia. Gomez runs late to Lopez' second meeting, having to calm him down before he meets the FBI. Once Chase and Lopez meets and he's shown the money, Castillo orders Lopez arrested, choosing not to risk letting him go. Lopez cooperates with the FBI and reveals that Garcia plans to rob and kill chase at their meeting. Scola and Tiffany rush to the rendezvous, where a shooting occurs after Garcia arrives. He is shot by Tiffany during it, and Gomez is wounded in the process, but survives. Scola sets out to ask Nina to dinner, hoping to mend their relationship, which she eventually accepts.

• This episode marks the debut appearance of Shantel VanSanten (Nina Chase).

After the murder of Tom Hamilton, a federal reserve security guard; the investigation leads the team to two unknown men who are in possession of a chemical weapon, sarin gas, an extremely toxic compound. The gas is odorless and colorless, due to its extreme potency as a nerve agent it is known and used as a chemical weapon. Wallace and Scola find one of the men, Nassar Ali, a known terrorist in Syria, and attempt to apprehend him, but are forced to kill him when he resists arrest. OA and Maggie go to an abandoned building belonging to Gen Research where the other man, Hakeen Abbas, and the sarin gas are located. OA and Maggie split up upon entering the building to cover more ground. Maggie finds Abbas, and tries to get him off the ledge but he pulls a gun on her, resulting in Maggie killing him. In the process, a canister with the gas falls on the ground, exposing the room, closing the doors automatically. OA, with the guidance of a doctor at 26 Fed, manage to get Maggie out, but her severe injuries lands her in hospital for an uncertain period of time.

With Maggie in hospital, the FBI's New York office investigate the murder of Maria Blake, who with her wife Olivia were attacked by an assailant who lurked into their home. Olivia survives and his hospitalised while her daughter Brooke is taken care of by child services. Nina Chase steps in as Maggie's substitute, and Castille is given a BAU supervisory agent to tag along. The team talks to carpenter Jeremiah Carver, who argued with Olivia prior to her death, having been fired. However he is soon cleared of suspicion, all the while the team realises that they're dealing with a serial killer targeting women in high ranking positions. Having obtain the Blake's surveillance footage, Castille decides to give the public the fragment of the killer's face it shows. They also identify glass from a church in his footprints, leading them to his sanctuary, where it's discovered that Castille is his next target. She manages to fend him off and reveals that he wears a silicon mask, and that he had white skin color and not black. Just as they determine that Olivia's ex-husband David Owen is the killer, Brooke is kidnapped from her school, fleeing to a family house in Bear Mountain Ridge. Owen holds his daughter captive and shows strong signs of going into a frenzy. Along with the SWAT team, the FBI sneak into the house from behind. OA talks Owen down while Scola and Chase flank him from behind, securing Brooke and arresting Owen.

TSA agent Cher Wilkins is murdered in an industrial area, with her supervisor having raised suspicions about her. The team apprehends Jorge Cissneros, who smuggled drugs through the airport to Chicago. Whilst watching Cissneros, OA sees someone who resembles a known terrorist he once hunted in Afghanistan, long believed to be dead. The first run is revealed to be a test, and they have him wear a wire for his second, which they discover is actually a bomb. Chase and other team members remain sceptical about said terrorist, Tamir Hazara, being alive, they also learn that Wilkins was on the restaurant owner, Jem Polat's, payroll. OA and Chase recon a restaurant Wilkins frequented just before her death, where OA confirms he saw Hazara. Polat is also discovered to be Afghani and whose name is an alias. OA has Ian look through restaurant surveillance and identifies Hazara with certainty that he is Polat's partner. Scola goes to the airport in Cissneros' place and identifies the new TSA guard on Porat's payroll to be Wilkins' supervisor, Bill Reynolds, who explains that his wife and son are taken hostage by Hazara. The team track his location to an abandoned industrial area, and has it surrounded. Knowing how Hazara operates, OA takes to the sewers with Chase to stop him. While she finds the hostages, he fights Hazara before killing him. In the aftermath, OA takes Chase's advise and decides to see a therapist.

Retired DEA agent Thomas Webber is gunned down right outside a local bakery. The FBI learns that he went on to work as a security guard at a nightclub, where he came into conflict with Rafer Boggs, who alleges that a girl he dated, cheated on him with Webber. Despite this, he is cleared of suspicion. Following the murder of Wallie Lamox, a church janitor, they learn that both him and Webber were considered witnesses against heroein gang LS-19, led by Callum Brewster. Tiffany asks Castille that they use one of Brewster's restaurant waitresses, Kayla Marsh, to get Brewster's phone, something she and Chase disagree on how to approach. They manage to convince Kayla, who successfully gets the phone for OA to clone. Texts on Brewster's phone confirms as the killer, in addition to ballistics on his gun. However, as they move into arrest Brewster, they discover him dead. Despite the initial promise to Kayla not to further involve her, Castille asks Tiffany and Chase to get her back on board to retrieve her boyfriend, Trey Copper's gun. Once ballistics is run on his gun, it's confirmed that it was the same gun used to kill the other victims. Tracking Cooper to a heliport, he takes Kayla hostage before being gunned down by Tiffany. Kayla is also arrested for having aided and abetting Cooper. Tiffany and Chase set aside their differences in the aftermath of the case.