Chicago Fire Season 11 Finale: Devastating Twist and Casey's Return.

In the season finale of "Chicago Fire," Matt Casey returns to Chicago after a bullet with ties to a militia group is found, indicating a potential domestic terrorist threat to the city. Jesse Spencer reprises his role as Casey, while Taylor Kinney, who plays Kelly Severide, will not appear due to a personal matter. Casey instructs Stella to inform her Department of Homeland Security task force contact, and he hops on a red-eye flight to Chicago to help with the investigation.