This is the full text of the novel Greenmantle by John Buchan, the second of five novels by featuring the character of Richard Hanna. Hannay is called in to investigate rumors of an uprising in the Muslim world and undertakes a perilous journey through enemy territory to meet his friend Sandy in Constantinople. Once there, he and his friends must thwart the Germans' plans to use religion to help them win the war, climaxing at the battle of Erzurum