Season 4 - Episode Guide

After a young woman is killed on her way home from a lavish yacht party, the team investigates who she was and how she came to be at the event, which was attended by some of the most influential people in the world. Also, Maggie brings Crosby into the investigation after a murder suspect is identified as a veteran who had been on several Army operations with Crosby.

Maggie, OA and the team must stop a hacker who is disabling life-saving equipment in several New York City hospitals, while demanding a full investigation into the recently deceased patients of a local psychiatric facility. With Jubal's son waiting for important surgery at one of the impacted hospitals, Jubal's adamant about remaining involved in the case despite Isobel's reservations.

After the team finds a connection between bombings at government agencies and a private veterans' club in New York City, Isobel tells OA to recruit his former Army buddy, Chris, for intel since he spends time at the club. However, knowing the difficulty soldiers like Chris often face returning to civilian life, OA is reluctant to follow orders.

The team hunts for a serial killer who is targeting young, homeless men. Also, Tiffany and Scola don't see eye to eye on how to handle the case or the difference between partners and co-workers.

After a suburban woman is kidnapped from her home, the team looks into trysts on both sides of a seemingly perfect marriage. Also, OA feels pressure from Mona to make changes in his career path.

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.

After a young girl is kidnapped from her daycare, the team must help her parents navigate a debt owed to the deadly gang in their neighborhood. Also, Maggie struggles to focus on the case when her sister, Erin, returns from rehab.

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.

As the team investigates a string of jewelry store robberies that culminate in a double murder, they uncover a connection to a 16-year-old boy trying to survive the foster care system. Also, Tiffany becomes personally invested after learning about the boy's ill-fated upbringing.

As the team searches for an abducted college co-ed, Jubal becomes intent on obtaining lifesaving leads from the father of the abductor's previous victim. Also, Jubal continues to grapple with the aftermath of Rina's condition, leading to a tense encounter with her mother.

Maggie goes undercover working in a bar to investigate an anti-government group that regularly gathers there and has several members suspected in a series of bombings. The case opens old wounds for her when a single father on the periphery of the group begins to fear he's in danger of becoming collateral damage.

When a Muslim college student and his younger brother are murdered, the team connects with the outraged imam of OA's former mosque, who insists the victims were wrongly targeted as terrorists. Also, OA must reconsider where his loyalties lie when working the case with a Muslim anti-terrorist agent bent on solving the investigation through any means necessary.

The team rushes to investigate an extremist gun group after an anti-gun lobbyist building is bombed, with the promise of others to follow. Also, SAC Bashar dangles a possible promotion for OA, but only if he can persuade Tiffany to not report an incident she viewed as misconduct.

The team realizes they have a cross-country serial killer on their hands, after another body is found bound with the same sophisticated knot as their local victim. Also, the case has ties to Isobel's father, Robert, and his hotel, leading to revelations about their fractured relationship.

After an ICE agent is fatally shot at an ICE vs. DEA hockey game, the team attempts to find the shooter who they believe may also be targeting Congressman Curtis Grange, who was at the same game.

When a young couple is found murdered in a New York City park after returning from vacation, the team searches for a suspect linked to the drug trade. Also, Scola turns over a new leaf when it comes to his relationships.

OA is forced to confront one of his biggest fears when the team discovers that deadly sarin gas may have been sold to terrorists.

When a morning show host is murdered inside her home, the team tracks the killer, who they realize is targeting powerful women. Also, things become awkward for Scola when Special Agent Nina Chase becomes part of the team during Maggie's recovery.

The murder of a TSA agent leads the team to hunt down a killer who is using drug mules to exploit airport security checkpoints. Also, OA struggles to cope with the aftermath of the sarin gas exposure and the 10th anniversary of his army friend's death in Afghanistan.

When a retired DEA agent is shot outside a bakery, the team works to determine if the victim's past cases or current bouncer job are connected to the murder. Also, Nina and Tiffany clash over the use of an informant while they are paired during the investigation.