A mysterious black aeroplane and a dastardly plot.

Forced down by thick fog, Biggles and Algy cut short a pleasure flight and land on a river in Norfolk to wait out the weather. Exploring the banks, they stumble across a wartime pillbox with papers written in German hidden inside! Shortly afterwards, a massive plane painted black to camouflage it against the night sky sets down on the water with a roar.

Biggles investigates, boarding the craft to find it is a bomber of immense proportions. He quickly finds himself in trouble when, becoming trapped inside one of the plane's compartments, he feels it take off with him still inside!

Who is the mysterious 'Blackbeard'? And why is he making secretive landings on the English coast? Biggles and Algy and introducing 'Ginger' Hebblethwaite for the first time must find out

Britain is under threat, and our heroes will answer her call.