After eight people are fatally poisoned at a deli in New York City, special agents Maggie Bell and OA Zidan trace the crime to an unlikely culprit and conduct a sting operation to prevent further attacks.

After a decorated FBI agent is murdered, the team investigates and uncovers the man led a double life. Also, Maggie struggles with what information she should reveal to the agent’s widow, who is also her personal friend.

The team welcomes a new member, Special Agent Tiffany Wallace, as they search for killers who orchestrated a mass shooting at a media company, and OA’s personal connection with the case threatens to cloud his judgement.

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.

As the team investigates a string of jewellery 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. Tiffany becomes personally invested after learning about the boy's ill-fated upbringing.