The ordeals of an elderly friend prompt Sully to consider his own loneliness; Alex regrets revealing that she discovered Jimmy on the eve of his wedding having sex with an old flame who happens to be Lombardo's current girlfriend after the news spreads like wildfire throughout the squad; Jimmy and Brooke get married.

Bosco, Yokas, Sully and Davis search for a cop killer on the streets, and cope with an obnoxious new sergeant at the station house.

A secret threatens to destroy Jimmy's relationships at work and home; Sully makes a date with his pretty neighbor; Bosco gets violent after his mother is beaten by her boyfriend.

Sully is upset when he is wrongly accused of falsifying evidence; Bobby helps one of his former teachers dying from cancer; Carlos deludes himself into thinking that Kim is falling in love with him; Sully gets closer to his pretty neighbor.

Bobby comes to the aid of his old friend Paulie after Paulie's sister begs Bobby to help her brother with his drug addiction, but becomes enraged when Paulie breaks into Bobby's mother's house and robs her to support his habit.

Faith and Bosco hunt down the dealer who distributed a batch of lethal heroin; depressed over Bobby's death, Kim attempts suicide.

Ty, Sully, Bosco, and Faith rush to the scene of a school shooting; Sully and Tatiana ponder their future together; Kim continues to struggle with her depression.

On September 10, 2001, Ty and Sully are in Atlantic City on the eve of Sully's wedding to Tatiana. Kim sinks deeper into depression. Bosco searches for anything to do after someone lets out the result of the Giants game he had taped to watch after shift. Jimmy keeps trying to catch up on some sleep after nursing a sick Joey.

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.

No one can find Bosco after a sexual assault suspect is found dead. While Bosco spends time with family, Yokas, Ty and Sully try to clear him as a murder suspect. Still locked in a custody battle over Joey, Jimmy and Kim meet with a court-appointed evaluator and plead their cases. Alex tries to stay busy to avoid dealing with her feelings about her father's death.

After seeing his young son Joey fall and break his arm in a playground accident, Jimmy fights through a burning apartment building to save a frightened boy of Joey's age. Meanwhile, a guilt-ridden Doc can't stay away from a recuperating teenager, Ryan Buckley, who was accidentally paralyzed while under Doc's care. Taylor is annoyed by a new probationary firefighter, Ken Prescott. Bosco and Yokas search for a drug addict who murdered his girlfriend.

Feeling betrayed, Doc angrily confronts his former friend, Jerry Mankowitz, an attorney's investigator who tricked him into confiding vital information about a pending malpractice suit.

The police officers sort through the carnage and count their dead in the wake of a shootout between rival gangs. While Faith tries to interrogate Fyodor Chevchenko, a ruthless Russian mob boss, Sully worries about the severely wounded Ty and regrets causing the incident. Tatiana chastises Sully for hassling her injured son. Faith worries about Gusler, her ineffective, frightened rookie partner and a weary Doc gets some unexpected, good news about his medical malpractice suit.

Tatiana is still missing, and Sully continues to search for her while grieving her loss. When he comes upon the body of a six-year-old girl in a box on a curb, he becomes strangely unnerved. Haunted by this sight and by thoughts of the mistakes he has made recently, Sully takes the rest of the day off sick and winds up in a local restaurant where he finds his parish priest. They ruminate on the nature of guilt, absolution, forgiveness, faith, and the intercession of God as they recall the fate of another man who also made mistakes and tried to fix them, and whose life ended tragically at Sully's hand. Sully finally comes to a place where he can forgive himself and go on with life. He seeks out Davis to once again beg his forgiveness and reaffirm their connection to each other.

When a doctor comes to New York to search for the missing daughter of her drug-addicted sister, Faith and Bosco focus their attention on the child's stepfather, a New Jersey cop, after they discover that the girl was taken by a man in uniform; Tatiana returns home; Jimmy spends some quality time with Joey.

The crossover starts on ER S08E19 Brothers and Sisters

Bosco roams the city looking for Faith, and finally tracks her down just as Faith manages to carry Fred out of the building after rescuing him from the elevator. After they race him to to Mercy, an overwrought Faith lashes out viciously and unfairly, first at Proctor and then at Bosco. As painful as her words are to hear, Bosco realizes the truth be

Bosco gets a temporary assignment working with a tough female sergeant; Fred is strangely calm in the face of the prospect of a triple bypass; Doc hears shocking news from Philadelphia; Sully learns more about Tatiana's past; Davis is forced to deal with his newfound fame.

Yokas and Bosco try to find a missing boy whose parents think has been taken by a registered sex offender; Sully prepares to be questioned about his wife's background

Doherty, riding on his motorcycle, is first to arrive at a multivehicle collision; Taylor is hit by a car; Tatiana goes to see Chevchenko, and tragedy ensues.

Chevchenko has Tatiana's son killed; Fred comes home from the hospital; and Davis gets a job offer.