In this meandering experiment in biography, the historian Linda Colley uses the fortunes of a “remarkable but barely known woman” to illuminate the buzzing circuits of trade and empire in the 18th century. The outline of Elizabeth Marsh’s story is exotic and spiced with danger. Born in 1735 to a family of Royal Navy men, she followed her officer father to Menorca, Spain, and was imprisoned en route by a Sultan in Morocco, a harrowing experience she recalled in “The Female Captive,” published anonymously in London in 1759. (Marsh was the first woman to write about Morocco in the English language). Later, she journeyed with her merchant husband to India, where she traveled extensively and flouted convention by taking up with a British soldier.

“The Ordeal of Elizabeth Marsh” (Pantheon, 303 pages, $27.50) is suggestive if occasionally muddled. Ms. Colley wants to get beyond the pale abstractions of history to show the effect of social and economic forces on flesh and blood individuals. The “socially obscure, sometimesimpoverished and elusively mobile” Marsh was buffeted by the currents of global change. “Elizabeth Marsh’s existence coincided with a distinctive and markedly violent phase of world history,” Ms. Colley writes, “in which connections between continents and oceans broadened and altered in multiple ways. These changes in the global landscape repeatedly shaped and distorted Elizabeth Marsh’s personal progress.” Through Marsh, Ms. Colley tracks not only a life story, but also a fraught phase in the evolution of global economics.

Ms. Colley has assembled an enormous amount of material for her book, which is spin-off from her last one, “Captives,” a dazzling account of Britons taken prisoner in India, Afghanistan, and elsewhere in the early years of the empire. With her new subject, Ms. Colley was forced to deal with a few impediments — no letters of Marsh survive, and there are no accounts detailing her appearance.

At times, Marsh is no more than a cipher for the historical trends of her time. But Ms. Colley is interested in something larger and more ambitious than mere portraiture. Marsh serves as an axis around which many lines of inquiry rotate. There are at least a dozen economic monographs in miniature on Ms. Colley’s pages, plus accounts of her subject’s extended family. She gives over many pages to Marsh’s father and uncle to show how the much Royal Navy determined the contour of her life. So we are lead to Jamaica, where her father, Milbourne, sailed on a mission to suppress slave revolts and fight off the Spanish, and where he seems to have met Elizabeth’s mother, who may have been of mixed race descent.

Then it’s off to Portsmouth, Britain, and Menorca for Milbourne, with young Elizabeth in tow. At 19, she set out for England, but her ship was intercepted by Moroccan corsairs. During her imprisonment, Marsh met her husband, James Crisp, an ambitious, enterprising man, who smuggled silks from Spain, salted fish in the Shetlands, and ran contraband out of the Isle of Man. His trading connections ranged from Hamburg to Livorno to Barcelona and his dealings give us a sense of the extent of the world economy in the 1760s.

The outbreak of the Seven Years’ War severely cramped Crisp’s operations, but he secured a position in the East India Company as a salt agent in Dhaka. Although Elizabeth followed her husband East, Ms. Colley speculates that their marriage was strained. When Marsh fell ill, she traveled south to Madras, where she entered into her unorthodox relationship with an army Captain. If Marsh comes off at times as the plaything of world-historical forces, her Indian travels show her as fully her own person. For a moment, she transcended her stations as wife and woman of uncertain status. “Elizabeth Marsh had incontestably passed outside the conventions of proper female behavior that pertained to her lifetime and after,” Ms. Colley writes.

Elizabeth Marsh died in 1785, and passed out of history. Ms. Colley’s resurrection leaves one with much to ponder to about fate, identity, and the meanings of history, but her book will not win any prizes for its style. Ms. Colley is a fine, even innovative scholar, but phrases such as “her father’s occupation also impacted on her in less enabling ways” are downright ugly. This might pass muster in a seminar room, but it’s unfortunate in a book from such a prestigious literary imprint as Pantheon. As they used to say in old newspaper days, “Get me rewrite!”

Mr. Price is a frequent contributor to Bookforum. He last wrote for these pages on Queen Elizabeth I.