Special Agent Scott Forrester and his Budapest-based FBI fly team head to Croatia, after Isobel Castille enlists their help to capture an American fugitive who escaped to Zagreb with a 14-year-old girl. OA continues with the mission overseas, intent on bringing the fugitive to justice, while Europol agent Katrin Jaeger attempts to help the team secure the necessary support and access from the less-than-cooperative local authorities.

The crossover starts on FBI S04E01 All That Glitters (I) and FBI: Most Wanted S03E01 Exposed (II).

The International Fly Team is called on when a young mother flees to Hungary with her son, after losing partial custody of her son in the U.S. However, after the boy is kidnapped from his mother in broad daylight in Budapest, the team questions which parent is the danger in the child’s life

The team investigates when the hijacking of millions worth of cryptocurrency en route to a safety vault in Switzerland leaves an American transporter dead and another on the run.

The team investigates an American citizen who is proclaiming his innocence after seeking sanctuary at Madrid’s U.S. embassy while still covered in the blood of his murdered Spanish boyfriend. Also, Vo and Raines continue to grow their friendship.

The team investigates an American journalist’s death by poison after his attempt to meet with an anonymous source in Poland. Also, Kellett takes Forrester to task for being overprotective with her during the mission.

After a U.S. intelligence negotiator goes missing and her ransacked Paris apartment is discovered to be covered in her blood, the team is on the clock to find her before the country's nuclear secrets fall into the wrong hands. Also, Forrester finds himself drawing certain parallels to his mother's disappearance.

When an American founder of an illegal adults-only site is killed in Prague, the team is tasked to locate his co-founder, who is still on the run in Czech Republic; Kellett struggles to maintain a relationship with her mother.

When a group of Americans are among the victims of a bombing at a festival in Budapest, the team is brought in to find the perpetrators before they strike again. Also, when Vo's new beau is injured in the blast, she re-evaluates what dating truly means while in the bureau.

The team jets to Bulgaria when terrorists hold hostage for millions in cryptocurrency a concert hall filled with multinational student performers and their families. Raines is intent on proving his field skills, and Forrester receives news of their dog, Tank.

Kellett and the team reluctantly join an investigation in Northern Ireland, when one of Kellett's informants is arrested for his connection to a robbery and murder, and calls her to help clear his name.

When an NYPD officer is detained in Transnistria for aggravated assault, the fly team investigates his claims of infiltrating a sex trafficking ring being concealed by those in power; Forrester receives an unusual message from an unknown sender.

When a notorious American tech tycoon becomes involved in a murder in Frankfurt, Germany, the team must chase him down amid the local protesters he's incited with his conspiracy theories on social media.

A couple flees to Albania while awaiting sentencing for bilking millions in COVID-19 relief funds from the U.S. government; Kellett works the case from Budapest as she and Forrester try to regain their professional boundaries.

The team must figure out how to keep the U.S. attorney general safe amid a possible security breach while she's in Hungary for an important meeting.

When Raines' sister goes missing in Kosovo, he goes rogue to find her, putting his job and his life on the line; Kellett and Forrester face further scrutiny from inside the bureau.

The Fly Team lands in hot water when Vo is found at the scene where a Hungarian gambling regulator was murdered.

When an American vintner is shot and killed on his wine estate in France, the team must determine if the region's local protest group with a history of violence against foreigners is to blame.

Following a frenzied attack by gunmen aboard an American-owned river cruise ship on the Danube, the Fly Team heads to Vienna to investigate why the boat was targeted. Also, Forrester realizes his feelings of mistrust caused by his past are affecting his personal relationships.

The Fly Team works to hunt down the sniper responsible for killing an American during an attack targeting a biomedical lab in Belgium. Also, Jaeger clashes with her boss at Europol over her allegiance to the Fly Team.

The Fly Team and Jaeger head to Berlin when the 19-year-old son of an American billionaire is found unresponsive in his apartment. As the team works to determine if foul play was involved, they realize there’s a shadowy group on the case as well.

When a private jet carrying American citizens is shot down outside of a small town in Poland, the Fly Team looks into the man who missed the flight. Also, Forrester is conflicted when he receives information from his mother.

The Fly Team and new Europol liaison Megan “Smitty” Garretson investigate when an American police detective on the Federal task force is murdered in Paris while looking into a U.S. company suspected of selling illegal weapons in France and the Middle East.

When a local predator begins extorting underage American girls online, the team attempts to bring the offender to justice with on-site help from one of the victims; Kellett decides she should find a roommate.

The team travels to Mallorca when an American is found brutally murdered on the estate of her powerful father-in-law.

When a former U.S. Marine is detained in Istanbul on a charge of smuggling antiquities, the Fly Team races against the clock to organize her release before the Turkish police learn the truth behind her visit

The Fly Team searches Bucharest for a Romanian surrogate who goes missing shortly before carrying the biological child of an American couple to term. Also, Forrester’s concern about the safety of his neighbors in Budapest intensifies.

Vo’s friend from the U.S. Navy calls in a favor to help find her missing nephew in Crete. Meanwhile, Forrester hangs back in Budapest to take care of personal business.

When an American businessman’s bodyguard and girlfriend are kidnapped a few feet away from him in Barcelona, the Fly Team questions if the man is as innocent as he claims. Also, Raines grows closer to Maya, the owner of the team’s favorite local bar.

Vo goes under cover when the team investigates the mysterious death of an American model in Milan; Kellett is caught off guard when Dandridge arrives looking for visibility on the case.

The team races through the streets of Budapest to put a halt to a major art heist about to be perpetrated by an American; Forrester grows angry as Dandridge watches every move the team makes.

When an American basketball player for a Lithuanian team goes into cardiac arrest, the team investigates along with Zoey McKenna, the new agent appointed by Dandridge.

The team races to find a kidnapped American teen in Austria as the clock ticks on Forrester's reassignment.

The Fly Team and Smitty reunite with Jaeger in Berlin as they all delve into a case involving an unidentified American who killed an elderly German man who appears to have been a covert asset of the ruthless Stasi in East Germany during the Cold War.

The team investigates the death of an American lawyer working out of Budapest, Hungary, after his is killed by a car bomb; Kellett begins to grow close to Hungarian lieutenant Benedek Erdős as the critical case progresses.

The team and Smitty head to Morocco when a commercial aircraft flying from New York to Athens is grounded and an American citizen on board goes missing; Kellett's relationship with Erdős continues to blossom.

The Fly Team lends a helping hand to the Hungarian National Police when one of their police officers is accused of murdering a couple in Budapest; Kellett questions her relationship with Erdős.

When the abduction of an American architect in Rome appears to be connected to a brewing terror threat in New York City, FBI’s Jubal and Nina join Forrester and his Fly Team in Italy as they work together to find the missing American and shed light on the terrorists’ U.S. target.

The crossover continues on FBI S05E17 Imminent Threat (II) and FBI: Most Wanted S04E16 Imminent Threat (III).

The Fly Team heads to Vienna to find the culprit of an acid attack on a rising American prima ballerina. Also, Smitty receives some troubling intel from a familiar face.

The team jumps into action to protect Forrester when a Russian hit man seeks revenge on him; Raines is sent into a tailspin when someone close to him is taken.

After an American tourist is killed while visiting Stockholm with his girlfriend, the Fly Team must work together to take down a Swedish group responsible for the hate crime.

After a cybersecurity expert robs one of Switzerland's largest and most secretive banks, the Fly Team is called to track down the fugitive. Also, Smitty's loyalty is put to the test.

The Fly Team jets off to Portugal when the daughter of a prominent American hotelier becomes the primary suspect in the murder of an employee. Also, Raines becomes concerned about Vo.

When a Russian missile is stolen and put on the black market in Budapest, the Fly Team must secure the weapon before a mysterious American arms broker delivers it into the wrong hands.

The Fly Team, with the help of their new intel analyst, Special Agent Amanda Tate, works to clean up the pieces left behind after a massive explosion rocks headquarters and their key suspect slips away.

When an ex-FBI agent suddenly resurfaces in a brutal Tripoli prison, Forrester and Powell risk everything to go under cover as prisoners to break him out; the fly team adjusts to their new and improved HQ.

When an American family's lavish sweet sixteen celebration is cut short after the mother of the birthday girl is found dead near their European estate, the Fly Team heads to Monaco to find the woman's murderer. Vo begins seeing Raines in a new light.

The Fly Team heads to Bulgaria in search of a wanted criminal who is exploiting underage American girls. Meanwhile, Raines becomes curious when Forrester asks him to keep an eye on Powell.

When a disgraced former U.S. cabinet member is arrested in Vienna, the Fly Team is sent to investigate whether he and his assistant were peddling classified government documents. Powell struggles as he is forced to stay behind on desk duty.

The Fly Team is called in to investigate when an American college student is arrested at a hostel in Prague for showing aggression toward local police who were dismissive of her sexual abuse claims. Also, Vo makes use of her sexual assault advocacy experience from her army days as they work to ensure the victim gets justice.

The Fly Team heads to the Tuscan countryside after an American couple's son is kidnapped right outside their new home. Concerns are heightened as fingers begin to point to the mafia.

Assistant Special Agent in Charge Jubal Valentine heads to Budapest to personally help the Fly Team and the CIA take down the cartel that murdered his former girlfriend and colleague. As part of the mission, Forrester poses as an undercover arms expert.

When a U.S. mercenary claiming to fight child trafficking abroad is apprehended at a remote Romanian border police outpost after the U.S. DOJ suspects his crew of embezzlement, Tate and Raines attempt to get him to flip on the leader of the group. The mission takes a turn when the outpost is attacked as they work to secure evidence.

When a wild night in Amsterdam for three ex-Navy men ends with one found dead in his hotel room, the Fly Team must dive into the red-light district to hunt down his killer. Meanwhile, Tate finds herself in a bind with her ex over custody of their daughter.

When a former member of the Irish Republican Army turned U.S. citizen is shot while in London with his son touring youth football academies, Smitty and the Fly Team work to hunt down the people responsible as the group becomes increasingly violent. While in London, Smitty pays a visit to her mother who she believes can help the team locate an old family friend who may have a connection to the case.

When the owner of a prominent cyber security company is murdered in Copenhagen, mass amounts of data are leaked, sending the NSA to the Fly Team for assistance, including the Bureau's liaison to the NSA.

The Fly Team heads to Oslo when they are tipped off that two Norwegian prisoners are being held in Russia.

The Fly Team meets Supervisory Special Agent Wesley "Wes" Mitchell when his partner is shot in LA and the suspects flee to Budapest, sending Mitchell overseas.

When a U.S. ambassador is taken hostage at a TV station in the Netherlands alongside 70 civilians, the Fly Team is forced to work quickly to find out who they're up against. Meanwhile, Wes works to earn the respect of his new team.

When an American teenager disappears from a beach party during her senior year trip to Portugal, the Fly Team heads up the search, which is further complicated by the missing teen's parents' differing opinions.

The deputy inspector general calls on Tate, who is fluent in Spanish, to take on her first undercover field mission, joining Wes and the team in Spain as they investigate a seemingly dirty U.S. Drug Enforcement Administration special agent working out of Madrid.

When an American man is kidnapped in Warsaw alongside a Ukrainian woman he met on a dating site, the Fly Team heads to Poland to track down the mastermind behind the site.

When a bus full of American volunteers is hijacked in a dangerous section of Morocco, the Fly Team works to locate the missing aid workers and the people who kidnapped them.

Wes' former colleague, U.S.-based agent Tyler Booth, enlists the Fly Team's assistance in helping him capture an American on the FBI's "Most Wanted" list by luring him out of Russia with the help of the perp's conflicted ex-wife.

When the star witness in the case against Greg Csonka, the man responsible for the death of Wes' former partner, is beaten to death in a Budapest prison before he can testify, the Fly Team attempts to salvage the case to secure Csonka's conviction.

A member of the Fly Team goes missing as the hunt for Greg Csonka continues in Paris. Meanwhile, Vo’s life hangs in the balance after being shot.

When a Russian biochemist is assassinated for trying to defect with his highly sensitive biotoxins research, the Fly Team springs into action to protect his daughter, whose father’s last wish was that she get his research to a trusted American microbiologist. Meanwhile, Mitchell stays behind to help Vo during her recovery, and Booth clashes with Smitty when he finds out she could jeopardize his promotion.

When an American student is found dead at a prestigious UK university, the Fly Team investigates an infamous secret society. Smitty’s personal history with the school comes to a head when she’s confronted with the same old-world elitism.

The Fly Team leads an international manhunt when an American woman and her new husband flee from Baltimore to Istanbul with her young son after a heinous murder. Also, Vo partners up with Special Agent Riley Quinn, who was not only sent to Budapest to work her first big case alongside The Fly Team but to also clandestinely investigate a member of the team.

When an American businessman is gunned down in Bratislava, the Fly Team must work with an unscrupulous local detective while safeguarding the sole witness, a fearful tourist from Wisconsin being held by police. Meanwhile, Quinn begins to feel pressure from her brother to deliver information on Mitchell.

After a young American woman is brutally murdered in Venice, the Fly Team is met with hostility when they discover that their person of interest has ties to a well-connected Italian family. Soon, the case gets even more complicated when the CIA Station Chief shows up with an agenda of his own. Meanwhile, pressure mounts on Quinn to deliver intel on Mitchell.

When a televangelist on the FBI’s most wanted list surfaces in Gibraltar to seek asylum, the Fly Team’s attempts to take him down hit a roadblock as they face political stonewalling upon arrival to the region. When the predatory preacher goes after the daughter of a disciple as his next target, the team must abandon protocol to intervene.

After an American CEO living in Prague is extorted for millions in cryptocurrency and his family is kidnapped, Mitchell receives a surprise visit from his ex-girlfriend, FBI Special Agent Ella Driscoll, who wants the Fly Team’s help on the case.

When a psychologist with national security intel goes missing on a hike in the Swiss Alps, the Fly Team works alongside a friendly face, Agent Tyler Booth, to find him. Meanwhile, Mitchell receives unnerving news regarding his biological father.

The Fly Team heads to the country of Georgia to determine the motive behind an attack that targeted two American soldiers at a NATO-Georgia joint training center before it turns into an international incident. Meanwhile, a supervisory position opens in another FBI division in Europe, and Mitchell encourages both Vo and Raines to apply.

When a suspected American arms dealer with a lengthy rap sheet pops up in Vienna with stolen weapons, the Fly Team sends Mitchell and Smitty undercover to try to infiltrate his operation. During the mission, Smitty enters muddy waters while working with the suspect’s wife. Meanwhile, Mitchell’s biological father shows up in Budapest after being released from prison to seek him out despite Mitchell’s disinterest.

When an American official in charge of a high-profile three-way prisoner swap in Belgrade is detained in Romania, he requests the Fly Team step in and carry out the exchange. When their convoy is attacked and one of the prisoners escapes, the team must do everything in their power to find the missing prisoner before the highly sensitive mission is compromised.

When an American student and sex worker is murdered in Budapest, similarities to a recent case in Japan lead the Fly Team to partner with detectives from Tokyo, on part one of the two-part series finale.

The Fly Team discovers they’re on the trail of a serial killer, taking the investigation, and Mitchell, to Japan to put an end to the international killing spree, on part two of the two-part series finale.