A known cartel fixer arrives in New York City, and as the team gets busy tracking him down, they discover the body of a dead DEA agent. After it becomes clear the case is not what it seems, the team must work quickly to prevent additional murders. Meanwhile, Bill makes a shocking discovery when he returns to work after the death of his father, and the team enlists the help of FBI's Special Agent Stuart Scola.
In order to stop a terrorist cell carrying out a chemical bombing at an unknown location in the city, the team joins forces with an old school code breaker who is suffering from agoraphobia. Together they decipher a seemingly unbreakable cipher. Meanwhile, Colin wrestles with Toni’s return to the field, and Bill braces for Katie’s response to his recent admission.