Biggles and the team are called in by Gaskin to get to the bottom of a series of cunning jewel thefts around London. He suspects aeroplanes are being used to fly the goods out of the country - which turns out to be correct.

Biggles and Ginger go undercover in an attempt to join the gang, even to the extent of faking a theft themselves. Their plan works all too well, finally getting them an audience with the illusive leader, at which he uncovers their true identities and locks them in a farm he then sets on fire. Thankfully Gaskin, Bertie, Algy and several hundred bobbies come to the rescue, collecting all the bad guys and saving the good guys to smoke themselves stupid on another day.