Greenmantle is the second of five novels by John Buchan featuring the character of Richard Hannay, first published in 1916 by Hodder & Stoughton, London. It is one of two Hannay novels set during the First World War, the other being Mr Standfast (1919); Hannay's first and best-known adventure, The Thirty-Nine Steps (1915), is set in the period immediately preceding the war. The book opens in November 1915, with Hannay and his friend Sandy convalescing from wounds received at the Battle of Loos. Hannay is summoned to the Foreign Office by Sir Walter Bullivant, a senior intelligence man, whom Hannay met and assisted in The Thirty-Nine Steps. Bullivant gives Hannay an outline of the political situation in the Middle East, and hints that the Germans and their Turkish allies are plotting to cause a great uprising throughout the Muslim world, that will throw the whole of the Middle East, India and North Africa into turmoil; Bullivant proposes that Hannay takes on the task of investigating rumours. The only clue he is given is a slip of paper left by a spy, Bullivant's own son, recently killed in the region, bearing the words Kasredin, cancer and v.I. Despite his misgivings and feelings of inadequacy for the task, Hannay accepts the challenge, and picks Sandy to help him. Bullivant tells him that an American, John Blenkiron, will also be useful to him. The three meet up, ponder their clues, and plan to head to Constantinople. They start on November 17, and plan to meet up in a rough hostelry there exactly two months later, going each by his own route - Blenkiron, as a neutral, travelling through Germany as an observer, Sandy using his contacts in the Arab world to make the journey through Asia Minor, and Hannay, taking on the identity of Boer "Cornelis Brandt," entering enemy territory via Lisbon. Arriving there, he meets by chance his old comrade from adventurous times in Africa, Boer Peter Pienaar, and together the two enter Germany via the Netherlands, posing as anti-British exiles itching to fight for the German side. They meet the powerful and sinister Colonel Ulric von Stumm, and persuade him they can help stir up the Muslim peoples to join the German side. The two are separated, and Hannay is introduced to a Herr Gaudian, famed mining engineer (who would later reappear after the war in The Three Hostages), hears of the mysterious Hilda von Einem, and has a brief meeting with the Kaiser. Finding Stumm plans to send him to Egypt via London, Hannay flees into the snowbound countryside, tracked by the vengeful Colonel. He falls ill with malaria and is sheltered over Christmas by a poor woman in a lonely cottage. On his sickbed, he realises that the clue "v.I" on the piece of paper may refer to the name he overheard, von Einem. Recuperated, he carries on, travelling by barge carrying armaments down the Danube, picking up with Peter Pienaar, who has escaped from a German prison, along the way. They pass through Vienna, Budapest and Belgrade, and as they travel, Hannay connects the phrase "der grune Mantel" with something else he overheard earlier. They reach Rustchuk on January 10, with a week to go before the rendezvous in Constantinople. On arrival there, Hannay has a run-in with Rasta Bey, an important Young Turk, and intercepts a telegram showing his trail has been picked up. They carry on by train, fending off an attempt to stop them by the angry Rasta Bey, and reach Constantinople with half a day to spare. They seek out the meeting place, and are attacked by Bey and an angry mob, but rescued by a band of mysterious, wild dancing men, whom they then antagonise. Next day they return to the rendezvous, an illicit dance-room, where they find the main entertainment is none other than the wild men of the previous day.