Hannay is called in to investigate rumours of an uprising in the Muslim world, and undertakes a perilous journey through enemy territory to meet his friend Sandy in Constantinople.

Entering Germany via the Netherlands, they meet the powerful and sinister Colonel Ulrich von Stumm, and convince him they can help persuade the Muslims to join the Germans' side.

They pass through Vienna, Budapest and Belgrade, and as they travel, Hannay connects the phrase "der grüne Mantel" with something else he overheard earlier.

On arrival, Hannay has a run-in with Rasta Bey, an important Young Turk, and intercepts a telegram showing his trail has been detected.

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 antagonize, inadvertently, because of a cultural misunderstanding.

At the climax of the performance, soldiers of the Ottoman Minister of War Enver, arrive and drag Hannay and Peter away, apparently to prison, but they instead are delivered to a cozy room containing Blenkiron and the leader of the dancers – none other than the miraculous Sandy Arbuthnot.

They pool their news – Sandy has identified "Kasredin" from their clue sheet as the title of an ancient Turkish allegorical story, the hero of which is a religious leader called Greenmantle, and has heard much of a prophet known as "the Emerald", associated with the play.

Blenkiron provides Hannay with a new identity, an American engineer named Hannau, and they attend a dinner party where they meet Herr Gaudian again, and Enver.

Sandy visits, agrees to deal with the captive Turk and provides news of his own – the clue "Cancer" means the prophet Greenmantle has the disease and is on his deathbed.

They form a plan to flee around the side of the battle lines, and while Sandy's helper searches for horses, Pienaar starts his dangerous mission.

Hilda von Einem arrives, and appeals to them to give up, but they refuse; she is shocked to learn Sandy is a British officer, and as she leaves, she is slain by a stray Russian shell.

[7][8] Peter Hopkirk's nonfiction work Like Hidden Fire, published in 1997, follows actual German plots to destabilise the region during World War I.

It was broadcast on BBC Radio4 Extra in two episodes on 27 and 28 August 2013, and again on 30 April and 1 May 2015, with David Robb as Richard Hannay and James Fleet as Sandy Arbuthnot, forced to be 'Greenmantle'.