Tessa Hadley, author now of eight novels and three collections of short stories, has few rivals in portraying the dynamics of families and the intricate weave of emotional affiliations among members. She is a genius at capturing fugitive thoughts and memories, the propulsive energy of desire, and the provisional reasoning that constitute inner being. Her plots, though often marked by a stunning revelation, are not where the dramatic action is; that occurs within the characters themselves. Her 2015 novel “The Past” is her masterpiece in this regard, not least in her depiction of the inner worlds of children, but her present...

Tessa Hadley, author now of eight novels and three collections of short stories, has few rivals in portraying the dynamics of families and the intricate weave of emotional affiliations among members. She is a genius at capturing fugitive thoughts and memories, the propulsive energy of desire, and the provisional reasoning that constitute inner being. Her plots, though often marked by a stunning revelation, are not where the dramatic action is; that occurs within the characters themselves. Her 2015 novel “The Past” is her masterpiece in this regard, not least in her depiction of the inner worlds of children, but her present novel, “Free Love,” approaches that work’s agility in capturing thought and feeling in flight. In this case, we have an English family in a moment of social upheaval remaking their lives, unyoking themselves from each other and from the conventions of the past.

The novel begins in 1967 with Phyllis Fischer dressing carefully for a little dinner she and her husband, Roger, are giving that evening. He is a high-placed civil servant in the Foreign Office; she is a housewife and stalwart of gracious living. They live in a charming Arts-and-Crafts house in a wealthy London suburb and are the parents of Colette, 15, and Hugh, 9. One guest will be coming: Nicholas “Nicky” Knight, a young man in his early 20s, the son of old friends of Roger’s parents. This is the first time the Fischers have seen him since he was a child—and we would not be surprised if it were the last. Arriving over an hour late, he is a sloppy, rude, insufferable prig. But Phyllis, at 40, is viscerally drawn to him, attracted by his disorderliness, by “his long hair, scruffy flared trousers, unbuttoned unironed shirt, drawling mockery, thin smiles, offensive opinions, deliciously offensive everything.”

Free Love

By Tessa Hadley

Harper, 287 pages, $26.99

For this is the ’60s. While Phyllis is more adventurous than members of the previous generation—she has Elizabeth David on the shelf and garlic in the pantry—something more potent is in the air. She suddenly feels that, in leading her comfortably ordered, bourgeois existence, she is missing out on life itself. She also wonders for the very first time whether she has genuinely become too old to possess sexual allure: Although “she’d begun joking recently about becoming an old woman . . . It hadn’t seriously occurred to her, in her deeper awareness, that anything had changed or must ever change; she’d take for granted that at her core her sexual self would continue for ever, a nugget of radioactive material charged with its power, irreducible.”

She needn’t have worried. Briefly alone with Phyllis, Nicky spontaneously kisses her and she responds vigorously. Enlivened by passion, she decides that he will be her lover, and so it comes to pass. Every Wednesday she takes the train to London to visit him in his squalid bedsitter in Ladbroke Grove. Rundown, littered with junk, and mutilated by demolitions preparatory to building an elevated highway, the area is daunting to her on her first trip: “She’d never seen so many coloured faces before, anywhere in England.” Scared, she feels “conspicuous in her beige mac, beige shoes, pretty mauve flowered blouse and silk scarf, chosen to be careless and joyful . . . It hadn’t occurred to her to imagine wearing them in a deprived area like this, where their expensive smartness seemed flagrant and ill-advised.” Later, as the trysts continue, she revels in the milieu and manages to fend off acknowledging the full moral significance of her infidelity: “She knew that her betrayal of her husband and children was wrong, but in the same impersonal dulled way that she knew from school about the Treaty of Vienna, or the abolition of the Corn Laws.”

Though not remorseful, she is, nonetheless, haunted by the specter of her other life, “conscious on those Wednesdays of her own absence, like a ghost in all those rooms which, in the past, she’d arranged so beautifully. Without her, the place fell apart . . . no one turned on the lamps she had placed around the rooms to give off their welcoming glow; everything was bleak in the glare from the main light.” Phyllis bucks herself up with a spate of annoyance that she is the only one who cleans up around the place, but this sense of doubleness pricks at her, the abandoned life that goes in her absence and the clandestine one she occupies. Eventually—and impulsively—she walks out on her family, out of her former life, and moves in with Nicky.

There are consequences, many and unforeseen, but this novel is not out to punish anyone; in fact, it is surprisingly kindly; we have here no “Anna Karenina” or “Madame Bovary.” Phyllis’s sporadic feelings of guilt, bitter though they are, are outweighed by her embrace of the ideas of personal freedom and fulfillment—notions that bloomed so extravagantly in the ’60s: “There wasn’t any point, she told herself, in thinking about the children. No reparation could be made for what she’d done. . . . The only thing to hang on to was that she must truly change, to give meaning to her betrayal. She had to believe that what Nicky awakened in her had sprung out of life itself.”

But what of Colette and Hugh and Roger? Their home has become a dismal, uneasy place. Roger is stoical; Hugh, who smelled a rat from the beginning, is angry and heads off to boarding school where he informs everyone that his mother is dead. Colette, a very bright, but rather dumpy girl, longs to become a new person, to transform herself into the exotic, seemingly self-contained people she sees as she wanders the London streets: “Young women passing her looked exactly as she wanted to look herself: dangerous and deadpan, in junk-shop clothes, cultivating fascinating inner lives.” Ms. Hadley perfectly captures this aspect of the ’60s, the urgency of wanting to join the paraded mystique and collective individuality of the beautiful people, so “nonchalant and oblivious, as if they’d been initiated into some code that others couldn’t break.”

The novel becomes Colette’s for a spell. She throws out her frumpy clothes, loses weight, and adorns herself with beads and whimsical outfits. She tracks her mother down and begins to gravitate toward the group of artists and writers—would-be for the most part—who make up her mother’s new friends. She attends a raucous concert held in a wasteland, but somehow, burdened by a reflective intelligence and acerbic temper, she can’t make the transformation to Dionysian: “Everyone else knew how to be carried along in this turbulent river, while Colette watched from the dry land of herself. She felt the river’s pull and its powerful romance, along with its terror, but didn’t know how to let herself into it.”

That is only to set the conditions for the complexities that ensue, including one hell of a development that, as Roger observes, creates a “situation as fatally twisted as a Greek drama.” Told chiefly from three viewpoints—Phyllis’s, Colette’s and Roger’s—“Free Love” is a penetrating, extraordinarily subtle novel about an unsubtle era. From a distance, its culture may seem to have been all surface: all sex, pot, fancy dress and political righteousness, but Ms. Hadley shows how it worked its changes into the lives and feelings of a handful of superbly conjured individuals.

—Ms. Powers is a recipient of the National Book Critics Circle’s Nona Balakian Citation for Excellence in Reviewing.