The team races to stop an active serial killer after three women are found weighted down at the bottom of a lake, and Jubal looks into an old closed case after there are multiple similarities to the recent victims.

After a bomb leaves three people dead, the team presses a reluctant informant to gather information from his close friends who are under suspicion. Also, OA finds tension in his relationship with his girlfriend, Mona, when they clash on where the informant’s rights lie.

When five prominent men are killed at a trendy New York City restaurant, the team’s investigation brings them into contact with a lieutenant in Antonio Vargas’ cartel, triggering a long-awaited showdown between Isobel and Vargas.

Maggie, OA and the team must stop a hacker who is disabling life-saving equipment in several New York City hospitals. Jubal's son waits for important surgery at one of the impacted hospitals.

The team finds a connection between bombings and a private veterans' club in New York City; Isobel tells a reluctant OA to recruit a former Army buddy for intel.

The team must track down a shooter targeting detectives from the same precinct and unit, while facing mounting tension from the NYPD. Also, Tiffany finds that her NYPD roots may be influencing her view of the situation.

The team attempts to extract key information from a vulnerable 9/11 widow, Hannah Thompson, who is shocked that her new “boyfriend” is the manipulative leader of a terrorist group planning an attack. Also, Scola is reminded of his brother’s death on 9/11, and Tiffany worries about his emotional choices during the investigation.

After Rina is critically wounded while heading to work with Jubal, the team makes the chilling discovery that a vengeful Vargas orchestrated the shooting from behind bars and continues to target the rest of their team and their loved ones.