Putting the Pieces Together in a Small Town : CAROLINA MOON by Jill McCorkle; Algonquin Books of Chapel Hill; $18.95, 260 pages

People in small towns only think they know everything about one another. They know something, of course, but it’s jagged-edged, like a jigsaw-puzzle piece--or like part of the torn-up suicide note Cecil Lowe left behind in Jill McCorkle’s fifth novel, “Carolina Moon.”

Cecil’s carpenter son, Tom, who was 10 when his philandering father shot himself, has carried most of the note in his wallet for 25 years. He has no idea that the missing piece is in the hands of Cecil’s former lover, now Tom’s employer, Queen Mary Stutts Purdy, who runs a smoking-rehabilitation clinic in Fulton, N.C. (Her advertising slogan: “Put your butt out and bring your butt in.”)

If either Tom or Quee, as she calls herself, knew what the rest of the note says, it would shatter a vast structure of memory and longing, just as Hurricane Hazel pulverized Cecil’s beach house and left Tom with property that’s dry only at low tide.

We know, of course, what both pieces say. The suspense lies in when and how Tom and Quee will find out. Meanwhile, we feel like God, in secret possession of the big picture. This has always been one of the chief pleasures of reading small-town novels, and McCorkle (“The Cheer Leader,” “Ferris Beach”) deals out that pleasure with an expert hand.

In the first chapter, for example, she has us look over the shoulder of an elderly postal official as he reads the latest in a series of anonymous, undeliverable letters, addressed only to “Wayward One,” that have been piling up in his office for those same 25 years. The postman-voyeur has identified the addressee as the dead Cecil, but who is this angry, inconsolable woman who writes him?

We figure out soon enough that it’s Quee, but this only introduces another puzzle: How does this jagged piece of her fit with the Quee we see in other contexts--big and lusty, a businesswoman in her 60s who has “never been weak a day in my life,” a benevolent meddler in Fulton’s affairs who is more than a little like God herself?

Among her helpers at the clinic is Alicia Jameson, long-suffering wife of Jones Jameson, the town’s tomcatting, trash-talking radio deejay. Jones’ disappearance at the beginning of the novel is hardly mourned, but the discovery of his corpse in a load of gardening topsoil delivered to rich, friendless Myra Carter is the mainspring of the plot.

Not in a murder-mystery sense--nobody much cares who killed Jones--but because all those puzzle pieces are forced at last to interlock.

In McCorkle’s world, a hybrid of romantic comedy and Southern Gothic, this frees her characters more often than it saddens them. Ignorance isn’t bliss, much less wisdom. Myra, for example, has fumed for years over the suspicion that her late husband, a doctor, hadan affair with Quee. Not true. He and Quee merely worked together as abortionists.

Across town, as Sarah McCallister lies in a stroke-induced coma, her lawyer husband, Mack, struggles with his attraction for her best friend, June, while wondering whether Sarah loved him less than her first boyfriend, handsome Tom Lowe. Meanwhile, Tom is falling for Denny Parks, Quee’s goddaughter and the clinic’s new therapist (whose tape-recorded musings are as pungent as Quee’s letters), and the widowed Alicia is being courted by Robert Bobbin, the nerdy sheriff’s deputy investigating Jones’ death.

So many stories, so little space. Dare we complain that McCorkle knits “Carolina Moon” together too quickly and neatly? It’s those odd-shaped pieces, after all, that give the puzzle its charm. We’re willing to be entertained by them a while longer. (When a character is introduced as the “Spandex Poet,” for example, we ought to see at least a sample of her verse.) So sure is the emotional tone here--sexy and sensible, warm and ironic at once--that we’re never in danger of letting the big picture slip by.