Peter Tolan, Leary's creative partner, describes the self-destructive Gavin as "a bottomless pit of disbelief in the goodness of people and of himself."
In a five-alarm twist, however, Gavin will crawl out of the pit this season, Tolan says. Last seen drugged and unconscious in the burning beach house of his spurned girlfriend, he'll see the light.
Before he reaches the promise of redemption, Gavin must hit "an extremely dark, disconnected place," Tolan explains. By the end of the season's 13 episodes, the change "will be fairly dramatic."
In a Dickensian conceit, Gavin's wake-up call takes the form of a surreal glimpse into what his future will be if he doesn't clean up his life, which as long as we've known him, has revolved around copulating, boozing, and avoiding the c-word - commitment.
"Through the actions of others or through visitations, Tommy sees what's awaiting him and all the guys in the [fire]house," says Tolan, 48. "He gets shaken up."
To Leary, his character "is visiting the deep recesses of his own wishes, and in the course of that, confronting his own fears, finally.
"Basically, it's a trip through the male ego - fear, death, grief and sex, and how they all work in the male mind. He's finally facing the fact of 'This is how I am and this is how I have to live in order to change.' "
Through all the upheaval, Gavin manages to stay on the wagon.
BTW, Leary, a recovered alcoholic, has no patience with celebrities who blame their bad behavior on the bottle.
For example, when Mel Gibson insisted that his anti-Semitic rant last summer was due to too much tequila, Leary ripped him in an original song with his rock band.
"If tequila made Mexico anti-Semitic, the entire country would be an anti-Jew zone," Leary muses.
"Don't blame alcohol. The truth is, when you're drunk, you have to take responsibility at some level. Don't say, 'It's the tequila's fault, not mine.' "
Speaking of responsibility, the symbolism of Leary's character's almost having died by fire is not lost on the actor.
The out-of-control blaze represents "a personal hell and a metaphorical hell for him. It's all about the getting out and the lessons he's supposed to learn."
In Tolan's view, the season finale "did smell of a traditional cliffhanger. There was some false jeopardy built into it. Obviously, we can't kill Tommy, but that doesn't mean we can't kill somebody else."
Set six months after the beach-house fire, tomorrow's season premiere opens with Gavin's world in its usual chaos.
He's being investigated by the insurance company for possible arson. He's living platonically with his ex-wife (Andrea Roth), helping her raise an infant who may be his - or his dead brother's.
Adding to the hormonal ambivalence, Jennifer Esposito (Crash) joins the cast as Nona, a gorgeous Long Island volunteer firefighter who dragged Gavin from the burning beach house. They may or may not be dating.
"She's the female version of Tommy," Leary says. "She's a chick who doesn't care about relationships. She just wants to have sex. She's tough. She loves to eat. It's his dream come true."
Also new to the lineup: Larenz Tate (a young Quincy Jones inthe movie Ray) as a stud basketballer recruited to Manhattan 62 Truck to play on its team. As part of his deal, he can't be called "probie."
With the chief (Jack McGee) recovering from a heart attack, there will be a rotating series of fill-ins, including Jerry Adler (The Sopranos' Hesh); stand-up Adam Ferrara, and Tolan himself.
From the beginning, Leary and Tolan figured Rescue would go five seasons. Now they're talking six, seven. Maybe more.
"We're still in love with telling the story," Leary says. "It continues to excite us."
"The scripts are flying out," Tolan says. "When Denis and I get together, it just pops. Why stop?"
Clearly, these two hotshots don't need rescuing.
Contact staff writer Gail Shister at 215-854-2224 or firstname.lastname@example.org. Read her recent work at http://go.philly.com/gailshister.