The king's mistress is dead. Who killed her? A jealous queen? A scheming noble hoping to foment civil war? Or was it an unfortunate accident? The stakes are high, and so the King sends his foremost medical investigator to unravel the mystery: an investigator who just happens to be not only a doctor and forensic scientist but also, most unusually for 12th-century England - a woman.
What sets The Serpent's Tale most vividly apart from other historical mysteries is the main character: the Italian-trained female doctor Vesuvia Adelia Rachel Ortese Aguilar who heals the sick and solves crimes with her forensic skills. This book is the second in the "Mistress of the Art of Death" series, and is well worth the read. The story is fascinating in its complexity and the atmosphere of 12th-century England is beautifully evoked. Historical celebrities like Henry II and Eleanor of Aquitaine appear, as well as interesting characters which include Vesuvia's companions: the eunuch Mansur and her friend, the prickly Glytha.
One of the most interesting aspects of the book is watching this woman negotiate the gender roles of medieval English society, which are more restrictive than those of her native Salerno. To avoid raising suspicion of witchcraft she has to allow the Saracen Mansur to play the role of the doctor while she acts as his "assistant", although it is actually she who performs the healing. Franklin does an excellent job portraying Vesuvia's frustration but also her practicality. She knows what needs to be done and makes her compromises, not always cheerfully but readily, putting the needs of the patient or the requirements of justice before her own ego. She is a very interesting and sympathetic character who makes this book and the others in the series well worth reading just to get to know her.
See also my colleague's review of the fourth book in this series: "A Murderous Procession".