The book explores the sexual revolution-era trend of "swinging" (partner-swapping) via a glimpse into the lives of two couples in a small New England college town who enter casually into such an affair, with disastrous consequences.

While doing research in Vienna, Austria, he met Utch, an orphaned survivor of the German occupation and the Russian siege at the end of World War II.

At the opening of the novel, the narrator and Utch are married with two children and live a relatively placid existence until, at a faculty party, they become acquainted with Severin Winter, a Viennese-born professor of German and coach of the school's wrestling team, and his wife Edith, a WASP from a privileged background (she met her husband in Vienna while on a buying trip for MOMA) who is an aspiring fiction writer.

The narrator had developed genuine feelings for Edith, and while she did seem to reciprocate them, at least to a small degree, he is left despondent after she ends their liaison to salvage her marriage to Severin.

The sport of wrestling featured prominently—the novel's title refers to the 158-pound weight class, which Severin considers the most elite competitive weight—and a subplot eventually emerges involving Winter's protégé, a peculiar wrestling prodigy from Iowa who transfers to Winter's college because of its superior biology department and becomes a pawn in the fallout of the two couples' swinging relationship.