For thirty years, Nizam al-Mulk ruled the Seljuq Empire, wielding more power than the sultans he served-until the fall night in 1092 when an assassin's blade struck him down on the road to Baghdad. Among the papers he left behind, an unpublished manuscript warned that "damaging and odious enemies" had infiltrated the government. "One will not know the extent of their intrigues and their ruses until I am gone." Determined to learn who was behind...