I've debated whether or not Greenmantle could be classified as a mystery. Set during World War One, it certainly revolves around one: who is Greenmantle and can he be found in time to interfere with German plans to use him in their bid to grab the middle east?
Richard Hannay, last seen just before the war in The 39 Steps and now a major in the Lennox Highlanders, is recuperating from shrapnel wounds suffered at Loos, as is his friend Sandy Arbuthnot. Anxious to return to the front line, they are instead asked to undertake a secret mission.
Hannay, Arbuthnot, and the "sedentary dyspeptic" American John S. Blenkiron, joined later by an old friend from Hannay's South African days, must find the mysterious Greenmantle and assess the situation so the British can take countermeasures. It is a matter of great urgency and no time can be lost. However, they must begin the task with no clues except three words scribbled on a piece of paper -- Kasredin, cancer, and v.I. In different disguises the men take separate roads to Constantinople where they will meet and begin their search, if they all arrive safely -- and it's a big if. Along the way they encounter dangerous enemies and life-threatening situations and must use fast thinking and physical daring to even get to Turkey to begin their quest in the first place.
My verdict: This novel mirrors a time and society where fair play, decency, and honour were important and practiced as far as possible even in wartime. Military and intelligence gathering methods have changed since that war and for the modern reader this gives Greenmantle a poignant air at times. Even so, it's a rattling good yarn, with plenty of action, excitement, and suspense, along with a dash of wit. Although I'd read the novel before, I still laughed out loud at the mental picture of Hannay in jammies and dressing gown when, due to circumstances, he is "left to receive my guest in a room littered with broken glass and a senseless man in the cupboard".
Etext: Greenmantle by John Buchan