Tommy comes to terms with the reality of his broken family as a result of a shocking experience with his father. When a freak accident occurs, Franco must make a life-changing decision, and Chief Reilly is forced to expose a family secret in order to save his career.

Tommy attempts to handle the insanity of his father while defending Colleen's new lifestyle to Janet. At the firehouse, Sean and Mike the Probie unknowingly launch a full blown wager among the crew.

When Tommy struggles to help Janet in a financial crunch, he must turn to his Uncle Teddy to help him out. The new female addition to the house fights to be accepted by the guys while they do everything they can to drive her nuts. Just as Mike is getting fed up from sleeping on the firehouse couch, he is offered a helping hand with a free place to stay... at a steep price.

While Tommy attempts to make reason of the chaos in his life, he continues to defy death while pulling dangerous stunts on the job. Lou admits his infidelity to his wife and receives an unexpected surprise. When tragedy strikes his family, Tommy must come to the rescue of his father.

When Janet needs more money to cover house repairs, Tommy turns to Uncle Teddy and his "little" friend to help him out with extra cash. When Franco's father has a stroke, Franco finds himself trying to juggle work and raising his daughter on his own. Meanwhile, a goodwill tribute to the firefighters lost in 9/11 goes awry and the firehouse is put in jeopardy.

The hockey game rematch between the NYPD and the FDNY is right around the corner and Tommy must figure out a plan to save himself from being pummeled by the cops who have it out for him. Tommy's relationship with Sheila is discovered by the guys and they must adhere to tradition to handle it in their own way. When Tommy is visited by his demons during a fire, Franco comes to his aid... with devastating results.

In an effort to get more time off to search for his wife and kids, Tommy joins the new firehouse’s Barbershop Quartet. Meanwhile back at the old station, Lou and Chief Reilly conspire to get Tommy back, but the rest of the crew has grown fond of his replacement.

Tommy asks his cousin for help in understanding the bizarre visions he's been having. The crew tries to help Laura understand the essence of male comaraderie.

Tommy has a chance at finding his kids with help from his oldest daughter. Chief Jerry asks his son for help when his wife's condition worsens.

Franco's addiction to painkillers has driven him to a support group to get help with his problem. A young boy clings to life after Tommy saves him from a fire. Jerry is introduced to his gay son's life partner.

Jerry forces the crew to attend a birthday party that his son is throwing for his boyfriend. Meanwhile, Tommy makes a move on Mariel after she tells him she might not be his half sister after all. Franco asks Laura to move in with him while Sheila tries to make Tommy jealous by showing off her new girlfriend.

Tommy starts taking Janet's antidepressants. When Sean meddles in Franco and Laura's troubled relationship he makes things worse. After a gay visitor, the crew wonders about Mike's sexuality.

Tommy lays off the antidepressants when he is kicked off the hockey team. Sheila asks Tommy to talk Damien out of being a firefighter. Meanwhile, when Franco sees Laura with another guy he gets jealous and Tommy's dad gets a surprise when he returns home from a three day trip to Atlantic City.

Tommy's sister suddenly shows up in town when their dad is about to inherit a million dollars. Tommy and Janet decide to renew their wedding vows. Meanwhile, Mike is worried when he finds a lump.

Tommy copes with a tragedy. Jerry must decide what to do when his wife's condition worsens. Sean has a crisis of faith. Lou learns some shocking facts about Candy. And the crew responds to a multi-level building fire with people trapped inside.

Janet decides to meet with Tommy after not speaking with him for months since the sudden death of their son. Uncle Teddy refuses to allow anyone to help him get out prison. Tommy is shocked when he accidentally discovers just who his nephew has been sleeping with.

Franco begins to fear he's becoming Alicia's boy toy, while Tommy finds a way to end the fling between Damien and his science teacher. The rest of the crew also face their own problems - Lou is becoming real unstable emotionally, the chief has financial problems, and Sean is afraid of Tommy finding out who he's been sleeping with.

After Sheila bumps into Johnny's ex-wife, Angie, Tommy seeks her out. Jerry and Rose spend a very romantic evening together, while Mrs. Turbody is in jail for statutory rape. This gives Tommy some relief but also new worries, and Franco loses his daughter, Keela.

While Tommy and Johnny have another encounter, Janet and Angie re-establish their acquaintance. Meanwhile, Sheila is unhappy when she sees Tommy and Angie together. Maggie wants to get back together with Sean. Mike hooks up with a woman at a bar, making his roommate, Chris, jealous. Franco finds out about Jerry's second job at the pub, and the money in the no-smoking jar goes missing.

Lou turns to new-age techniques in his efforts to change his life. Sean and Maggie come to a surprising decision. Tommy and Angie continue to see each other, which quickly leads to an embarrassing scene with Janet.

The crew faces more than accustomed when rescuing a man from his burning apartment; Sean has a request for Maggie's dad; Franco thinks his new girlfriend is hiding something from him; and Tommy realizes that his crew's future together may be in jeopardy.

Following a meeting with Janet, Tommy has yet another confrontation with Johnny; Teddy's conjugal visits with Ellie prove to be a letdown; and Franco tries to befriend his new girlfriend's mentally challenged brother. Elsewhere, Tommy keeps his vigil at Stack's bedside.

John Sr. ends up disappearing after arguing with Tommy about their living conditions. Tommy is none too thrilled with Lou's latest love interest, while Jerry's new woman might prove to be dangerous for him. Also, Sean and Maggie meet with the priest to discuss their upcoming wedding.

Tommy and Janet are brought together once again by another Gavin family tragedy. Jerry ends up not showing up for work. Mike decides it is time to look for some advice about his sexuality. Meanwhile, Maggie has a surprise for Sean.

Sheila lies to Tommy when he confronts her about the beach-house fire. But they present a united front to the insurance investigators, as embarrassing as it is for Tommy. Meanwhile, Lou is determined to get a basketball ringer (Larenz Tate) to be 62 Truck's new probie; Uncle Teddy is released from jail; Colleen runs away with her rock-musician boyfriend; and Mike's mother has a deathbed request.

Tommy encounters Colleen's boyfriend and sparks fly; Jerry learns he flunked his physical and is given a desk job; Uncle Teddy, hiding from Ellie, breaks into prison guard Lenny's apartment; Sheila goes out with the man who pulled her from the beach house, while Tommy keeps avoiding Nona (Jennifer Esposito), the volunteer firefighter who rescued him from the blaze; and Mike seeks Tommy's advice on how to deal with his dying mother's request that he kill her.

The firehouse gets a new chief (Jerry Adler), who is rumored to possess a very special gift; Tommy suffers embarrassment during a hockey game against the NYPD; Franco works up the nerve to propose to Natalie while Sean tries to talk Maggie out of a divorce; and Sheila makes a surprising proposition as Janet's depression deepens.

The Gavin clan stages an intervention after several disturbing family calls; the mysterious woman (Gina Gershon) from the restaurant leaves Tommy wanting more; Janet must take matters into her own hands to get her baby back; and a depressed Mike calls Tommy in a moment of despair

The Gavin family AA group's first meeting doesn't go exactly as planned. Tommy bribes Colleen for information on Janet. Franco learns the truth about Natalie from Richie while Lou contemplates revenge on Cousin Mike.

Tommy goes on another memorable date with Beth for the sake of the crew; Black Shawn proves himself in an unexpected arena; Franco realizes what he's really lost while Latrina shows she knows how to keep Lou happy; Dad gives Tommy some insight into his childhood

Tommy plays hero in someone else's uniform, confusing the crew; Colleen finds a new reason to get upset with Tommy; Natalie asks Franco for a favor; a rift between Mike and Black Shawn nearly leads to blows; and Tommy makes a move on the chief's daughter. This does not please the chief.

In the fourth-season finale, Sheila learns that Jimmy's ghost has been spotted on several occasions, so she investigates. Meanwhile, Colleen blames Tommy for her failed relationship; Franco and Natalie come to an understanding, as do Lou, Cousin Mike and Latrina; and Tommy spends time with his father.

Tommy copes with the loss of his father and a new man in Janet's life. Sheila finds a different way to deal with her issues while Sean, Franco, and Mike concoct a surefire way to get rich and laid.

An exotic visitor sparks mixed reactions in the firehouse. Tommy deals with the possibility of expulsion from the FDNY and a new sponsorship role in AA. As Mike and the guys renovate their new bar, Sheila learns that being a big sister isn't always easy.

Tommy and Janet attempt to survive a weekend together at Katy's new prep school. Meanwhile, Lou sees Tommy's absence as a way to move in on Genevieve. Teddy and Maggie receive vulgar propositions and Sean's stomach pain acts up at an inopportune moment.

A late-night cleanup turns into a nightmare for Tommy when several unexpected visitors stop by the bar. Feinberg allows Damien to ride along with the crew, but may not be prepared for the consequences.

Tommy and Mike must find a way to mend their fences at work; Sheila tries to get Tommy to control his drinking with her leverage; Lou must relive an unpleasant memory; Franco heads back to the boxing ring; and Sean has his heart-to-heart talk with his mother.

Though Tommy's pacts with Sheila and Janet have begun to unravel, there is one Gavin who remains sexually adventurous much to Tommy's chagrin. Garrity divulges his medical secret, Tommy proclaims he's been drinking at AA, but its Mickey who will offer the final surprise.

After dealing with a particularly horrific accident on the job, Tommy questions his feelings in a dream sequence with his dead father, brother and son, and Jimmy Keefe. Meanwhile, Sean has an unwanted visitor at the hospital; and Lou has a very-much-wanted visitor to his apartment.

An outburst lands Tommy cleaning duty as a mysterious woman strolls through the firehouse; the Gavins confront Tommy about his alcoholism, but their plan does not unfold as expected.

The perfect party becomes a nightmare when a herd of brutish women infiltrate the bar. Tommy's love triangle reaches new heights.

A no-nonsense woman, looking for a date, shows up at the firehouse talking trash; Janet offers Tommy an ultimatum; Needles and Lou concoct a battle of the sexes; Sean's medical condition moves lower on his body.

Damian receives an offer that unsettles Tommy; Lou discusses his upcoming wedding plans with Tommy and Needles.

Tommy has rocky encounters with Janet and Sheila, and an encounter with Kelly that isn't as rocky. Meanwhile, the guys go grocery shopping with the newly domesticated Lou.

Franco steps into the ring with one of Carla's friends;Tommy tends bar after a failed rescue leaves the crew in the dumps.

Uncle Teddy appears surprisingly stoic after a staggering personal loss, but finally bursts at the seams and has the gang cornered. Janet and Sheila's plan goes haywire and leaves a trail of destruction in its wake.

A terrifying vision of the afterlife leaves Tommy shaken as he attempts to reconnect with his friends and family back on the outside. At the firehouse, the crew’s fate hangs in the balance when the department decides to cut costs.

With Damian confined to a chair and a new baby on the way, Sheila and Janet join forces and shake-up Tommy’s family life.