Biggles and the team are set the impossible task of tracking down a secret aircraft that regularly flaunts the law by landing and departing illegally, under cover of night.

The suspicious death of a policeman in the same area of the West Country where the plane comes and goes from, gives the team their first clue. They then proceed to unravel a rotten Lord and his money-making venture flying escaped criminals out of the country. This is not before Bertie has finally proved his worth with some fascinating insights into the growth cycle of heather.

In the end, the pilot and plane are captured, and the ringleader admits all before spectacularly, and messily, commiting suicide with a shotgun.