A Mercy sees America's last Nobel laureate for literature weighing in with her first novel in five years and returning to some of the themes explored in her most famous work, Beloved. Toni Morrison's ninth novel concerns the lives of four women on the Virginian property of an Anglo-Dutchman, Jacob Vaark, and their struggles in an era unfavourable to women, black or white. It is the late seventeenth century. The women are "orphans, each and all" and their fates, crucially, are subject to "the promise and threat of men". The slave trade is in its infancy and Jacob considers himself above such commerce, but on a whim he accepts an eight-year-old black girl called Florens as part-payment of a debt. This is the title's ambiguous act of mercy and the desperate act of a mother hoping to save her child, the consequences of which are tragic and unforseen.

Smallpox ravages the farm eight years later. Jacob dies; his wife, Rebekka, falls ill; and Florens, by now 16, is dispatched to locate a free black man who is known to be able to cure the sickness and with whom she is smitten. This journey forms the spine of A Mercy, and the narrative cycles between her first-person account of her travels and events as seen by the other characters.

This is a superior yet flawed historical novel, written in language largely sure-footed and occasionally beautiful. Rebekka fled religious persecution in England; a Native American woman, Lina, escaped the smallpox infection that devastated her tribe; and Sorrow survived a shipwreck. It is fertile ground, but while each woman has an interesting tale, none - aside from Florens - has much to do in the present of the story. As a result the novel lacks momentum, and the characters struggle to engage with each other and the reader. Florens' voice is idiosyncratic, veering between twee ("Hunger trembles me") and lyrical, but the other characters bear traces of research and too often their life stories groan beneath expositional digressions into the burgeoning sugar trade or gruesome punishments in merry old England. A Mercy illuminates some dark corners but is less successful as a novel about people attempting to keep their heads above the tide of histories, both personal and otherwise.