Christina Schwarz proved herself as one of our most intuitive and nuanced portrayers of relationships with her first two novels, “Drowning Ruth” and “All is Vanity.” She’s a master at revealing the turmoil lurking beneath the banality of everyday life, someone who can draw poetry from the murkiest linguistic well.

Her latest effort, though, “So Long at the Fair” (Doubleday, $24.95), turns out to be a puzzling, disjointed and nearly emotionless disappointment.

The book, told over the course of one long summer day in Madison, Wis., focuses mostly on Ginny and Jon, a long-married couple whose union is threatened by his dalliance with a co-worker, Freddi. Jon had planned to take Ginny to a summer fair. When her work as a landscape gardener interferes with the day, he seizes the chance to see Freddi instead.

Schwarz interweaves the present-day story with that of Jon’s and Ginny’s parents, who in 1963 were involved in a possible crime, and attendant revenge, that continues to wreak havoc on the now-grown children’s lives, sometimes in ways they can’t see coming.

The problem is that the reader can see those “surprises” from a mile away. The big book-ending denouement is telegraphed almost from the first page; another “cliffhanger” at the tale’s conclusion draws no stronger emotion than “oh, whatever.”

Schwarz’s gift with language hasn’t waned, and she occasionally inserts a bit of humor. “What was an appropriate gift for people who married after living together for twenty years?” Ginny ponders at one point. “Champagne, probably. Or aspirin. His and her revolvers.”

The author’s psychological insight also remains strong, as when Jon pictures his feelings for Ginny as “a root ball, the tough strings of love tangled with those of dependence and habit; the whole, heavy mass clotted here and there with disappointment and accommodation, as well as satisfaction and joy.”

But Schwarz has hung her lexical talent around the necks of people we don’t care about. If you want to read Schwarz at her best, go back to her debut, “Drowning Ruth.” Then hope that she gets her groove back with the next one.