Sammy Baker’s Ventura Squadron had everything going for it — brand new planes, top-line aircrew, the lot. So how come they got hacked out of the sky on nearly every air raid? The answer was obvious — there had to be a spy on the station, telling the enemy when the raids were coming.

But who was the spy? And how quickly could they find him? Because until they did, every raid was doomed, right from the moment of take-off!