A witness in a former case of Erin's, asks her for help shutting down a drug operation in his apartment building, she makes it her mission to make the building safe for his family. Also, while investigating a teen's suicide, Danny and Baez uncover information that suggests the death was a homicide, and Frank looks into potential misconduct in the Mayor's office.

When Danny intercepts a shipment of several million dollars that was heading to a drug cartel in Mexico, he becomes a target when they come back for revenge. Also, Jamie works independently to track down a serial killer who preys on the elderly, and Mayor Poole confides in Frank that he plans to retire.