Biggles starts an airline to transfer gold shipments, following requests from Raymond (now Assistant Commissioner of Police at Scotland Yard) to stop a series of thefts.

Using his natural cunning, Biggles manages to thwart the bad guys a few times, before the ringleader (the old friend Von Stalhein) ups the ante by kidnapping Algy and locking him in a castle in Germany. Biggles and Ginger come to the rescue, eventually, returning the team and its goods to London.

On their return the final piece of the puzzle falls into place, when one of Biggles employers is exposed as a double-agent, giving Von Stalhein's men the tip-offs needed to capture the gold and precious stones. However he's also been double-crossing Erich, who responds by shooting him dead and disappearing off back to his base in Germany.