Critically burned and with only hours to live, Lt. Johnson begs Doc and later, Jimmy to end his suffering. Mrs. Johnson flips out on her husband's coworkers, asking them why this happened to her husband and why they would want to do such a dangerous job. While on-route to another hospital and with Doc and his wife by his side, Lt. Johnson once again begs Doc to "help" him. Meanwhile, Kim finds out that Aaron is dead, Faith goes into surgery for her wounds, Bosco tells Swersky what happened in the hotel room and then talks to the FBI.

Kim discovers that her former lover was a drug user. A new paramedic starts, who Doc blames for Alex's death because she was covering the paramedic shift the new guy never showed up for. Bosco tries to get Faith out of trouble for shooting Cruz. Alex Taylor's funeral is held.

Yokas clashes with her mother-in-law over her recovery. Cruz is back on the job, but unhappy that she's back in patrol uniform. Ty and Sully discover a truck carrying sick illegal aliens and the police end up scouring the city to track down one of them who escapes after it's suspected that the aliens may have a highly contagious and potentially fatal disease. Ty is surprised to see his former girlfriend as an assistant district attorney involved in the case.

Jimmy struggles as Acting Lieutenant. Bosco and Monroe deal with a rapper causing problems. Ty is thinking about law school again. Faith is not making any progress with her recovery.

Bosco, Ty and Sully attend a rally where a judge's car is bombed. Sully is subsequently chosen for her protection detail. Cruz wants out of uniform and plans a sting operation in a brothel but gets raped. Faith is back in the hospital. Her doctors think her disability is psychogenic.

Judge Halsted's housekeeper is killed in the blast. The judge is determined to preside over the proceeding dealing with a motorcycle gang leader, who is also revealed to be responsible for Cruz's sister's death and the meth lab explosion. Monroe orders a rape kit for Cruz. Yokas sees a psychotherapist.

Sully shoots the detonator out of the hand of Frank Morgan, the bomber and Davis kills one of his partners; Doc goes ballistic when he comes upon the scene of an accident involving his old rig and a city bus, and physically assaults Eugene. Public Morals raids Dr. Chow's office, and Cruz is forced to reveal her rape to keep Thomas Warner from being released. Ty gets Frank Morgan to flip on Gary Barnes, and Barbara promises Morgan that she will make sure he gets the death penalty for killing her housekeeper and driver. Kim and Carlos refuse to back up Eugene after he files a complaint against Doc, prompting Eugene to quit. A distraught Faith, still plagued by flashbacks of the shooting, asks Fred if they can get out of the city for a family vacation. Warner confesses to raping Cruz while Bosco is transporting him to jail. Carlos is horrified when Doc admits that he accosted Eugene at his house because he "killed Taylor". Bosco turns Warner over to Cruz, who orders gang members to assault Warner in jail. Barbara rolls up to Sully's favorite diner on her motorcycle and joins him for coffee. Bosco softens his attitude toward Cruz.

Doc is demoted back to the streets and continues his downward spiral, presenting Kim with no end of problems as he lies about his demotion, resists her orders as the supervising paramedic, and deliberately runs down a perp with the bus. Barnes is stabbed and killed at Riker's for betraying Buford. Carlos is devastated when Kylie is diagnosed with a rare case of hereditary aplastic anemia and he's not a match for a bone marrow donation. Sully tries to deflect Ty's teasing about his relationship with Barbara by getting him to focus on their LSAT preparation. After an intense gunfight, Cruz finally captures the leader of the drug gang responsible for her sister's death.

As Carlos desperately searches for a bone marrow match for Kylie, he digs deeper into his own past and discovers that he wasn't abandoned by his parents, but was found clinging to his dead father's hand after a car accident. After a local station picks up the story, Carlos gets a call from a woman claiming to be his mother. Bosco and Monroe find themselves going after a small-time mobster putting the squeeze on an honest family-run linen company after the son of the linen company owner dies in a suspicious fire.

Bosco arrests a pedophile posing as a toy store Santa, and the grateful store owner returns the favor by helping Bosco and Sasha come to the aid of a man whose house is robbed of all his children's Christmas presents. After Sully and Ty save a young homeless girl from a fire, she rekindles Sully's Christmas spirit. Carlos receives the ultimate Christmas present when his brother arrives at the firehouse bearing the gift of being a perfect bone marrow match for Kylie, as well as the news of Carlos's real name and family history. Kim and Jimmy spend a romantic Christmas Eve together. Sasha's search for the perfect gift for her nephew gives Swersky the opportunity to play Santa.

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.

When Monroe discusses taking the sergeant's exam with Sgt Cruz, Cruz reveals that she received her promotion meritoriously, not from passing the test. The police are on high alert after two women are assaulted and robbed by men posing as police officers. Later on at the hospital one of the victim dies from their wounds. Kim and Jimmy decide to keep their blossoming romance quiet until Kim is pulled over by the impostors and narrowly escapes with her life with the help of Bosco, Cruz, Sully and Monroe.

Jimmy proposes. A new Captain arrives at the fire house and promotes Jimmy to a Rescue Squad in another house. Cruz extracts a murder confession from a man who Monroe saw elsewhere at the time of the crime.

Steeper orders the paramedics out of the house. Bosco finds out Allie Nardo has visited his mom, Rose. Nardo then sets up Bosco to make it look like he was taking a bribe. Bosco retaliates by setting up Nardo to look like an informant in front of his boss. Doc invites Christian for a ride-along, without telling Kim or Carlos. Doc spends the shift inviting all the cops, paramedics, firefighters and everyone at the hospital to a party at his place. An OCB detective informs Bosco that there was a shootout involving the mob boss and Nardo, who is now in the wind.

Steeper continues his by-the-book command style and goes head-to-head with Kim when Doc doesn't report for duty on time. Sasha can't find her off-duty weapon the morning after Doc's party. Faith returns to duty at the front desk despite Fred's wanting her to remain on disability, and discovers that Bosco has lied to her about Swersky's not allowing them to be partners. A panicked Nardo kidnaps Rose and then Bosco in a futile attempt to prove that he wasn't a rat, and makes a shocking choice when he realizes that his days as a mobster have come to an end. To the horror of the squads, Doc takes extreme measures to prevent Steeper from closing the house, and forces Carlos and Kim to risk their lives to do the right thing. Sully returns a favor by reaching out and saving his friend's life in Doc's hour of greatest need.

The investigation into Doc's actions starts. Rose invites Bosco to dinner, unbeknownst to him, with his brother. Fred is upset that Faith is partnering with Bosco again. A dead body is found, signaling that a drug war is starting. Cruz is miffed at being left out of a raid.

Questions are asked about why Cruz and Dade were watching Bosco's brother. Autopsy reveals that Dade was poisoned by Teflon on the bullets. Bosco searches for Mikey. Mikey says he was the driver, but not the shooter.

Distraught over losing an appeal to her suspension, Sasha gets into a car accident that claims the life of a young child. Sully and Ty take the L.S.A.T. Tensions flare between the cops and the firefighters when Maritza goes after J.D., the probationary firefighter, who turns out to be an ex-cop who ratted out Maritza's former partner for stealing drug money. Faith and Fred are still at odds over her return to work. Walsh is promoted to lieutenant. Ty watches over a devastated Sasha, who's racked with guilt over the car accident, Doc's shooting spree, and the events surrounding the deaths of Tanzi and Nardo. J.D. gives Faith and Bosco important evidence he discovered as he put out the fire resulting from Sasha's car accident, which leads the cops to uncovering the basis for the accident and exonerating Sasha.

Wary of Lester Martin, the high-priced lawyer his father has found for Mikey and the deal he's attempting to broker, Bosco warns his brother to stay away from Maritza. Mikey decides to disregard his brother's advice and makes a deal to become her informant. For good measure, Bosco threatens to kill Maritza if anything happens to Mikey. Sully teases Ty about his budding relationship with Sasha. Faith and Bosco strike a deal with Laura Wynn of Narcotics, who also has no love lost for Maritza, to protect Mikey by helping her nab the drug dealers before Maritza gets to them. J.D. offers Kim a ride home, but stops off first at a rave that both Anti-Crime and Narcotics have staked out, thanks to information Mikey gave them. When some bad ecstasy begins to take a rapid toll, the paramedics call for backup, which prompts Maritza and her detail to storm the building. After an arsonist lobs a Molotov cocktail into the crowded building, Faith and Bosco give chase and capture him, while the firefighters rescue the ravers who are trapped in the fire. Recuperating in the hospital after J.D. rescues her from the burning building, Kim realizes that he is intimately involved with running the rave, and threatens to report him, but he resigns first. Faith threatens to report Maritza to I.A.B. after the sergeant assaults Bosco and Faith's handcuffed prisoner and breaks his nose. Lester reappears in the station house, this time representing the arsonist, who's also eager to work out a deal by giving up the head of the ecstasy ring. Faith picks out a photo of Joey Mann, who drove the arsonist to the rave, and Laura identifies him as the son of Donald Mann, the head of the ecstasy ring. Maritza spooks Joey as she's about to arrest him, and they head off in a high-speed pursuit which narrowly avoids a group of children and leads to Joey's death. Laura warns Faith and Bosco that Donald will be after them to avenge his son's death.

Tensions still run high in the Yokas household. Lester preps Bosco for Mikey's hearing and then pulls a switch when he cross-examines him on the stand, leading to Mikey's getting released. Sully realizes what a toll the job has taken on him by his reaction to the deaths of three people in a robbery at the restaurant where he eats breakfast every day. Faith and Bosco answer a call which leads them to Lester's house, where they find his daughter not breathing. Sully tracks down and arrests the restaurant murderer. After Dr. Hickman tells Faith and Bosco that Lester's wife and daughter have been severely beaten, Lester is arrested. Sully gets his LSAT results. Ty and Sasha get closer.

Sully and Ty discover a torso and a hand in the trash. A new medic joins the team. Faith sits vigil with Rebecca Martin and tries to understand how a mother could allow this to happen to her child. Mikey is located. Bosco blames Lester and Cruz for what happened to his brother. Faith and Sasha find out what really happened to Rebecca. Faith receives an unpleasant surprise when she gets home. Donald Mann arrives in New York.

Faith pleads for her marriage. Bosco prepares for his brother's funeral. Donald Mann's plan for revenge on the police who were involved in his son's death is set in motion. Narcotics receives a tip about a container full of drugs and Anti-Crime raids an apartment. A car bomb is sent to Mikey's wake where Sully, Faith, Ty and Sasha are paying their respects to the Boscorelli family.