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 Among the papers he left behind, an unpublished manuscript warned that "damaging and odious enemies" had infiltrated the government.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 the murder of his chief minister, but unable to trust his officials, the sultan turns to one of the smartest people he knows: Omar Khayyam-astronomer, mathematician, poet, scholar of shari'ah, and lover of wine.With little experience navigating the dangerous waters of court politics, Omar must race to solve the mystery against the background of a Muslim world on the verge of fundamental change.