After a park ranger is shot dead by a masked assailant on Governors Island, the team discovers a string of connected crimes that leads them to their toughest roadblock yet: an online conspiracy theory community.

The investigation into an assistant U.S. attorney's death leads the team to a related airline whistleblower scandal and the chilling discovery that they don't have much time to thwart terrorists from crashing numerous in-flight commercial airplanes. Dealing with the memory of his brother, who was a 9/11 victim, the case pushes Scola hard to prevent another catastrophe.