One man. Two wives. Many secrets.

1858: Heiress Eleanor Fairley marries Connor Blake, a heroic veteran of the Crimean War. Only after he takes her to the isolated estate of Sterne House does she begin to realize that he may not be what he seems—and that she herself may be no more than a stepping-stone to his true ambitions.

1860: Connor Blake, now a widower, marries penniless beauty Cecily Jaine. In the imposing surroundings of Sterne House, Cecily senses everywhere the presence of her predecessor. The more she learns about her husband's first wife, the more she suspects that even in death Eleanor's fate is closely entwined with her own...and that Cecily herself may be in grave danger from her husband.

A Dangerous Observer alternates between the stories of Eleanor and Cecily, two women separated by time but united by the enigmatic man they both married—and the house that keeps their secrets.