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).