Pawn in frankincense1969
by Dunnett, Dorothy.
Somewhere within the bejeweled labyrinth of the Ottoman empire, a child 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 a pawn in a cutthroat game whose gambits include treason, enslavement and murder.
— from OpenLibrary
12 editions at OpenLibrary