Biggles turns double agent!Biggles is in London on leave from the Front when he is approached by a stranger who greets him as 'Captain Brunow'.Curious, Biggles plays along with the mistaken identity, and is quickly offered the chance to become a spy for the Germans!Reporting the encounter to Air Staff Intelligence, Biggles is encouraged to seize the opportunity and find out all he can about a German known only as El Shereef, operating somewhere in PalestineBiggles soon finds himself in Zabala, a German aerodrome in Palestine, reporting to Count von Faubourg of the German Secret Service and his chief of staff, one Erich von Stalhein the first appearance of Biggles' greatest nemesis.As Biggles draws closer to unmasking El Shereef, at all times he must ensure his own identity is never revealed, or he will be shot as a spy. A tense, thrilling Biggles espionage adventure in the deserts of the Levant.