Greenmantle is a classic espionage and adventure novel written by John Buchan. First published in 1916, the storty is set during The Great War, featuring the reckless Richard Hannay. Tasked with unraveling a mysterious message, Hannay travels through Germany and the Middle East, searching for the elusive religious leader ''Greenmantle''. Sequel to The Thirty-Nine Steps and precursor to Mr. Standfast.