Biggles goes undercover and joins the spy world in Palestine.

Mistaken for another whilst on leave in London, Biggles reports the confusion to Headquarters. To his chagrin they 'encourage' him to take the place of his doppelganger and work for the Germans as a spy whilst secretly reporting to the British.

As always, Biggles succeeds admirably. However there are a few close calls and nervous moments. Not least because Biggles has his first run in with Von Stalhein. Erich is working for German intelligence and comes close to unmasking Biggles on several occasions.