It is September 21, 2001, and the squads continue to battle through their emotions and their misgivings about their hero status, while working double shifts and spending every free moment at "the pile" searching for the missing. Kim returns to work and teams up with Doc, which allows an emotionally frayed Alex to return to paramedic duty; an exhausted Sully attempts to co-exist with his prospective in-laws while he waits for an opportunity to marry Tatiana.

Bosco tries to protect an old ESU sharp shooter from spiraling out of control. Faith contemplates taking the sergeant's exam. Davis and Taylor have a steamy affair. Doc feels the guilt over a mistake that made a boy a paraplegic.

Bosco and Monroe investigate a suspicious man who they find bleeding in an alleyway as they respond to an anonymous caller's claim that someone is shouting for help in the area. They become more and more skeptical when his story continues to change and they find a blood trail. When it is determined that the amount of blood would have been more than enough blood loss to kill a person, Bosco suspects that the man murdered someone and was bleeding because the victim tried to fight back.

Faith begs Fred to return home, but he refuses for a reason that infuriates his wife; Bosco turns a cold shoulder to Maritza's attempts to offer her condolences; Carlos is spectacularly unsuccessful in his attempts to hit on Grace; on the day of his son's funeral, Donald Mann exacts his revenge with the help of a dirty cop by planting bombs designed to kill the police officers he holds responsible for the death of his son; after Mann's lieutenants force a man to crash a car carrying a live bomb into the funeral home where Mikey's wake is being held, Grace takes charge and goes out of protocol to save Rose's life, and Dr. Fields later swears to have her job for it; Kim's decision not to enter the funeral home while the bomb is still live stems not from cowardice, but from maternal instincts; when Mann discovers that some of his intended targets survived the bombings, he sends machine-gun wielding minions into the hospital to finish off the job.

Cruz teams up with Rice to track down the terrorists associated with the possible dirty bomb.

The series concludes with the gangbangers taking out their assault on the 55th Precinct. After some grenade explosions, the precinct is destroyed. Cruz knows that Marcel Hollis is behind the attack, and she takes his life, as well as her own. Carlos proposes to Holly, and they are married. Everyone receives their reassignments, and Sully retires. In the last few moments, Sully narrates a look into the future.