Pawn in Frankincense (Lymond Chronicles: Book 4) by Dorothy Dunnett
Combining all the political intrigue of Game of Thrones with the sweeping romanticism of Outlander, Dorothy Dunnett's legendary Lymond Chronicles have enthralled readers for decades and amassed legions of devoted fans. In this fourth book in the series, Francis Crawford of Lymond embarks on a desperate and deadly journey in search of his kidnapped child.
Somewhere within the bejeweled labyrinth of the Ottoman Empire, a little boy is hidden. Now his father, Francis Crawford of Lymond, soldier of fortune and the exiled heir of Scottish nobility, is searching for him while ostensibly engaged on a mission to the Turkish Sultan. At stake is the political order of three continents, for Lymond's child is a pawn in a cutthroat game whose gambits include treason, enslavement, and murder. In the game's final move, which is played inside the harem of the Topkapi palace, Lymond will come face to face with his most implacable enemy, and the dreadful ambiguities of his own nature.