After Danny witnesses a drive-by shooting, he butts head with the detective assigned to the case; a childhood friend of Jamie's is convinced that she has single-handedly solved a cold case murder.

Jamie faces backlash from fellow officers when he partners with Erin and Anthony to investigate an underground bar the NYPD and FDNY use to hide their criminal indiscretions; Eddie's partner considers leaving the force.

Erin is stalked by a man who was recently released from prison; Jamie works to save his badge when he is caught driving under the influence after he is unknowingly given drugs at a party; Frank navigates multiple family issues.

Frank announces he will not endorse Erin's run for district attorney; Danny and Baez investigate a bloody crime scene at a hotel; Jamie begins a new job as a field intelligence sergeant that requires him to keep secrets from his family.

Danny reunites with Mickey Patrick, his childhood friend and a former criminal, who comes to him for help finding his missing fiancee; Anthony surprises Erin with one last stakeout before her run for district attorney.