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.