Tears of Pearl by Tasha Alexander

Emily has just remarried and is on her honeymoon in Constantinople with husband, Colin Hargreaves. When a young women, Ceyden, from a harem is found murdered, Emily and Colin are asked by the victim's father to find the killer. Emily goes between the palaces of Topkapi and Yildiz questioning servants and the women of the harems. She finds most of the women tight-lipped, yet is able to find out some details about Ceyden's life. Emily also encounters Roxelana, a woman who wants her help in escaping the confining life of a harem. In this fourth book of the Lady Emily series, Alexander brings the role of women in the Ottoman empire in the late 1800's to life.