There was an important reason why Scott Forrester (Luke Kleintank) left FBI: Internationalafter season 3. For the first three seasons of the police procedural, Forrester was the head of the elite Fly Team, which investigated international crimes that threatened the safety of the United States or violated the rights of US citizens living abroad. Like most shows in the One Chicago universe, it has had its fair share of cast turnover, though Forrester was a constant presence until near the end of season 3.