By Susan Isaacs. Scribner. 382 pp. $26

Nobody does smart, gutsy, funny, sexy dames better than Susan Isaacs. Her novels are the literary equivalent of a Myrna Loy movie, except that Isaacs's typical heroine is an up-from-the-working-class Jewish gal whose self-deprecating humor and wry view of social pretense betray an unease with the WASP world of privilege that the shiksa Loy's characters never felt.

The latest terrific Isaacs novel, Any Place I Hang My Hat, confronts, more directly than any of her previous books, the psychological fallout from a classic Isaacs family situation: that of a daughter who parents her parents. Isaacs's dames almost always have more on the ball than their fathers and, particularly, their mothers. Examples of this mother-as-child turnaround in her fiction range from the painfully prosaic (a mother with Alzheimer's disease in the murder mystery After All These Years) to the extraordinary (an alcoholic and promiscuous dumb bunny of a mother in the superb World War II suspense story/social drama Shining Through.)

Her latest heroine, Amy Lincoln (yes, she's Jewish, despite that moniker), boasts more than the usual quota of deeply flawed parents and guardians. She all but raised herself in a low-income project in New York City. Her paternal grandmother was her legal guardian, but the late Grandma Lil (who worked for years as a "substitute waxer, ripping the hair off the lips, legs, and random chins of the famous and the merely rich at Beaute, an uptown, upscale beauty salon") was not, as Amy admits, "the brightest bulb on the menorah."While she was growing up, Amy's loving screw-up of a dad, Charles "Chicky" Lincoln, was gone a lot, sojourning in the slammer for robbery, assault and other missteps. Amy's mother, Phyllis, who's the object of Amy's fantasies, was a teenager when, according to Lincoln family lore, she called out to her baby daughter, "See you later, sweets" and walked out the apartment door, never to return.

Still, through hard work, brainpower and a talent for ingratiating herself with powerful people, Amy has made something of herself. During her student years, a sympathetic social worker helped her get a scholarship to Ivey-Rush Academy, a tony girls' boarding school that was out to diversify its student body. ("Once I got there I realized that about two-thirds of the nonwhites in the [school brochure] photo must have been hired for the day from some Diversity, Our Specialty model agency.") Currently, the 28-year-old Amy works as an associate editor at a serious (no gossip, no photos) political magazine called In Depth. ("If In Depth had an escutcheon, it would bear the words NULLA SCIENTIA SINE TAEDIO on a field of bleakest gray. No knowledge without boredom.")

The plot gets rolling when Amy shows up at a snooty fundraiser for Sen. Thomas Bowles of Oregon, an outside candidate for the Democratic presidential nomination. The event, hosted by a men's footwear magnate and his missus at their mammoth Central Park West co-op, is disrupted when a young man dodges security and announces that he's the senator's out-of-wedlock son. Although the story lies outside her journalistic purview, Amy finds herself drawn to the plight of the party crasher. His desperate need to make contact with his alleged biological father reawakens Amy's nascent longings to find her mother.

Thus ensues a search that roams from the Royal Athens Diner in Queens ("The sort of place with a menu longer than the complete works of Dickens"), where Amy grills a reluctant "Chicky" about the details of his brief marriage to her runaway mother, to a gated retirement community in Florida where Amy tracks down her maternal grandmother. Her yearnings to find a family of her own are intensified by a painful breakup with her longtime boyfriend, by the unreliable companionship provided by her much-married best friend, "Tatty" (a society cake decorator), and by Sept. 11. Like so many other New York writers, Isaacs clearly feels compelled to register the horror of that day, but she wisely does so with restraint.

"How the hell can someone not have any feeling or . . . even curiosity about a human being he [or she] was responsible for giving life to?" That's the central question of this merrily observant, moving -- and, as always with Isaacs -- very entertaining novel. Sen. Bowles's supposed son shouts out the question directly; Amy asks it silently and constantly as she penetrates the mystery of her mother's disappearing act. Any Place I Hang My Hat testifies to the importance of family in an uncertain, sometimes terrifying world. Refreshingly, the novel expands its understanding of family to include those bound together by affinity as well as blood. *

Maureen Corrigan, who teaches literature at Georgetown University, is the book reviewer for the NPR program "Fresh Air."