Sarah Hall's ruminative fifth novel, "The Wolf Border," follows Rachel Caine, an estranged zoologist, as she navigates the precarious boundaries of intimacy. At the request of Thomas Pennington, the Earl of Annerdale, Rachel flies to her home village off the northwest coast of England. The earl wants to reintegrate the gray wolf, a species that's been absent from the region for hundreds of years.

Wavering at his offer to make her project manager, she visits her dying mother, Binny, a feisty, "self-declared, red-blooded sensualist." Soon after Rachel returns to Idaho, Binny commits suicide, and, after a one-night stand with her co-worker, Rachel becomes pregnant.

She harbors the secret, believing "romance fails because it is never supposed to work, past the act itself, the momentum of lust." After skipping Binny's funeral, Rachel is fueled by a sudden urge to reconcile with her half-brother, Lawrence, so she accepts the earl's offer.

Rachel contemplates an abortion, recalling the discombobulation of her own childhood. The project distracts her, and she enters a kind of limbo. Her life runs parallel with the wolves' reintegration: The wolves mate and relearn to hunt; she slowly makes herself vulnerable to the wildness of human relationships. She has a casual, mutually respectful romance with a veterinarian, Alexander. She decides to keep the baby, and a lot of page time is taken up with vivid snapshots of pregnancy and early infancy.

Hall's ever-present penchant for painting the landscape is in full force here, the lyricism reminiscent of her descriptions of the mist-soaked English seaside town of her second novel, "The Electric Michelangelo": "The leaves are sibilant in the breeze, and the head of the moon looms on the horizon like an alien silo." These moments signal the changing of seasons, the inevitable evolution of all things living.

Like Rachel, the book keeps the reader at a distance. Her sudden motive to reconcile with Lawrence is a tad blurry. How did Rachel become the cold half-prodigal she is? Rather than penetrate Rachel's interior, Hall seems to want us to understand Rachel via the wolves' reintegration, which has a surprising and satisfying end.

Where does freedom end and wildness begin? Self-preservation and intimacy? Sex and commitment? These are the gray borders Hall inspects. Despite the subplots about political protests and Lawrence's addictions and unsavory groundskeepers, the real story is the one about one woman's coming to terms, not only with her family, but with her own untameable nature.

It's a quiet inner odyssey that eschews the conventional standard of plot and instead forges itself incrementally, in beautifully sculpted prose.

Josh Cook's fiction and reviews have appeared in the Iowa Review, Thirty-Two Magazine, the Millions and elsewhere.