The corrupt, licentious court of England's James I makes a fittingly baroque backdrop for "A Net for Small Fishes," Lucy Jago's novel (based on an actual 17th-century scandal) about a complicated female friendship fueled by ambition and anger. When narrator Anne Turner first lays eyes on Frances Howard, in January 1609, she sees a weeping 18-year-old covered with welts after being whipped by her husband. These are of no concern to her mother, who has summoned Anne to dress Frances for a court appearance and coldly advises her daughter to "submit to your marriage," which was arranged to serve the political interests of the powerful Howard family.

Her 17-year-old husband beats her because he has been unable to consummate their union, Frankie confides. "I am very unhappy," she whispers, slipping her hand into Anne's. "In that moment, I recognized Frances Howard to be the dream I had long held," Anne tells us. "With Frankie, I could have the life I had always wanted."

Anne schemes for her family to surmount Jacobean society's rigid gradations of rank and status. Her husband George's medical practice at court requires the couple to spend money they don't have to keep up appearances; payments for the herbal medicines Anne concocts and the outfits she designs for court ladies help, but the couple is perennially in debt — not unlike Frankie's family, except that the Howards' spending is on a vastly greater scale and the nobility are rarely forced to pay their bills.

Anne is more fortunate than Frankie in one sense. George, impotent for some time, gracefully shares Anne with a lover, a courtier who fathered the three youngest of her six children; their marriage remains loving and supportive. Anne hopes that Frankie's patronage will smooth the path toward a knighthood for George and upward mobility for her children. Driven by a mixture of self-serving calculation and genuine tenderness for a girl half her age, Anne runs increasing risks as the novel takes a leisurely course toward disaster.

Jago weaves an intricate web of social, sexual and political maneuvers that entangles all her characters. Even Frankie's abusive husband is depicted with a measure of empathy as the traumatized son of a man executed for treason.

The Howards, arrogant and ruthless, are the target of poisonous anti-Catholic sentiments inflamed by the attempted assassination of the king and his ministers four years earlier. (Readers lacking a degree in English history, relax: It's not necessary to know precisely what historical events Anne alludes to in order to follow the plot, and Jago provides a helpful list of "the principal actors.")

Jovial King James, with his disarming Scottish accent, keeps his courtiers in debt and at each other's throats to buttress his power; his queen seethes over his homoerotic infatuations, accepted by the privileged elite that pays lip service to religion but not-very-covertly pursues every kind of illicit pleasure.

Anne is our guide to this decadent society, a wonderfully complex, not entirely likable character who shrewdly observes other people's missteps but is sometimes maddeningly oblivious to her own failures of judgment. (Refusing to see her aristocratic lover's weaselly nature is the prime example.) After her husband dies, constrained by law to leave the bulk of his property to their hostile eldest son, her desperate circumstances lead Anne to reluctantly enable Frankie's increasingly reckless behavior.

She wants more than the bold outfits Anne fashions to slyly assert feminine power. (Clothing is a resonant metaphor in Jago's able hands). Frankie has fallen in love with Sir Robert Carr, who despite being King James' handsome favorite seems equally enamored of Frankie. She pleads for Anne's help to get free of her husband, and Anne persuades herself that employing an alchemist is "no sin." She can't help but love this entitled beauty who "treat[ed] me as an equal and a friend, although I was neither."

In fact, Anne and Frankie become intimate friends during their dangerous quest to seize their desires in a world where women are expected to passively accept their lot. They will never be equals, however; Jago makes this brutally clear when they violate Jacobean society's cardinal rule: Don't get caught.

When they do, the consequences for Frankie are very different from those suffered by Anne. She remains loyal nonetheless to "the greatest friend of my life" and proudly declares "joy at the actions we took, the chaos we created, the possibilities we saw, the lives we led."

(This proto-feminist fervor will not seem anachronistic to anyone familiar with "The White Devil" and other gleefully antisocial Jacobean dramas.) An epilogue brings Anne's and Frankie's daughters together three decades later to affirm that their friendship was a defining moment in both women's lives.

That relationship is the unifying thread in a dense narrative stuffed with vividly drawn secondary characters and atmospheric set pieces that include a gruesome bearbaiting and a visit to an elaborately depraved brothel. Uncompromisingly dark though it often is, "A Net for Small Fishes" is also highly satisfying entertainment.

Wendy Smith is the author of "Real Life Drama: The Group Theatre and America, 1931-1940."

A Net for Small Fishes

By: Lucy Jago.

Publisher: Flatiron Books. 352 pages, $26.99.