In the late autumn of 1889, the body of an unknown woman appeared on the banks of the Seine River in Paris. It was taken to the city morgue behind Notre Dame and put on display for a month, according to protocol. The eerie beauty of the young woman's expression attracted crowds but no claimant, and so, before the body was dispatched, a mold was taken of the face, yielding a mask which was to become one of the most celebrated cult objets/curios of the 20^th century.

Set during the final days of the Paris expo of 1889, Brooks Hansen's The Unknown Woman of the Seine sets out to solve the mystery of who the woman was behind the mask. In charge of that investigation is a former Gendarme and recent prisoner of war just returned from Tonkin, China. Henri Brassard is on his way to Paris, determined to reclaim his place in La Force when he crosses paths with a mysterious and unnamed young maiden and her gypsy wagon. Detecting villainy, and bent on proving himself to his former superiors, Brassard tracks her into the city and observes from the shadows as, with evident but inscrutable purpose, she wends her way into the orbit of several savory and unsavory characters--an Artist, an Impresario, a Madame, a Countess, and one Disciple even--each of whom sees in her some opportunity, a chance for profit or redemption; any one of whom may therefore be responsible for her sudden and unexplained disappearance.

On that account, Brassard's chase will lead him on a grand tour of the city's lushest and seamiest venues, from its highest spires down into its darkest, dankest catacombs and past a gallery of equally diverse crimes--the moral, the political, the maniacal. By the end, he will, in fact, learn the stunning truth of the unknown woman's true identity, her past and present, but not before unearthing the equally disturbing truth about himself, who he has been, and who he must become.