His Dream of a Perfect Life Goes Up in Smoke : HOUSE ON FIRE by Denis Hamill; Atlantic Monthly Press; $22; 353 pages

The authenticity in Denis Hamill’s third novel is something we feel rather than see. We bark our shins on it, as if stumbling over heavy old furniture in a burning building filled with smoke.

We feel that authenticity when the hero, Kevin Dempsey, a Brooklyn firefighter, works two extra jobs to buy a $289,000 house for his wife, Polly, a British-born ex-model, and their 3-year-old daughter, Zoe. Waiting to surprise them with the purchase when they return from Disney World, Dempsey envisions a future of “six, maybe even seven children . . . fighting and playing and growing up all around him. . . .

“The Dempsey boys would be honor roll students and Golden Gloves champions and Zoe would be the first woman mayor of New York. . . . There would be no limits. . . .

“This was going to be the Place, the house where Kevin did his most important work in life. As a husband and father. As a man.”

Hamill (“Stomping Ground,” “Machine”) knows his New York Irish-Americans, their strong family ties, their two-fisted working-class pride, their sentiment. A Daily News columnist, he knows New York voices: black; Italian; Jewish; the classic, vanishing Brooklynese. He knows the neighborhoods, from crack-riddled slums to enclaves of century-old mansions.

But when Dempsey’s world collapses, the smoke of melodrama gets in our eyes.

It’s all so sudden and complete. Polly disappears with an unidentified lover, taking Zoe with her. She tells Dempsey that the child isn’t his. Dempsey’s doctor and boyhood pal, Anthony Scala, confirms this: Dempsey has been sterile ever since a bout with the mumps as a teenager.

In anguish, he drinks heavily, “freezes” when his partner is injured during a fire, and winds up in rehab, being counseled by an attractive young woman, Gail Levy, who hacks away at the macho underpinnings of what he had thought was the way every guy ought to be.

Meanwhile, Dempsey’s older brother, Frank, a cop, is rapidly drinking himself to death after being accused of stealing $1.5 million in drug money from an evidence locker. Their father, a retired cop, has committed suicide out of shame--hanged himself by the rawhide strap of his old baton. The youngest brother, Mike, also a cop, has been suspended for fighting in defense of the family honor. The sister, Margie, is too busy taking care of her siblings to have a life of her own.

All the Dempseys collaborate in the search for Zoe. As the plot, with its multiple secrets and betrayals, swirls from a Broadway dance audition to a medical convention in Boston to a fat farm in Arizona to a hilltop in Malibu, we bump into another big chunk of authenticity: the details of Frank’s alcoholism--even brushing his teeth makes him throw up--and his joy in working one last case, without a badge, to help his family.

But it’s a bit too much to expect us to believe that Frank, jaundiced and drowning in vodka, could attract one of the world’s most glamorous women just because he’s a nice guy.

And Kevin Dempsey, supposedly your average working stiff, is well-read, a short-story writer, a perceptive art critic. He’s killer-handsome, athletic, with a history of dating cheerleaders and starlets. The plot requires him to be, at various times, bright, stupid, brave, paralyzed, loving, violent, sensitive, obnoxious, irresistibly sexy and terrified of women; the impression isn’t of a complex man so much as of the author covering a whole lot of bases.

This becomes clearer when the story leaves Brooklyn and hurries, with a stark insistence and lack of subtlety, into the maw of the Mother of All Fires--when Zoe’s fate literally dangles from a balcony in Topanga Canyon ignited by blazing Santa Ana winds.

Nothing but smoke there.