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

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.

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 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 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.

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 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.

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 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 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.